## 1.

The Correct Answer is (C) — When dealing with these types of graphs, find the value you’re given on the appropriate axis (between 10 and 15 on the y-axis in this case), follow a line perpendicular to the axis until you intersect the curve, and read the value on the other axis. According to Figure 1, when the age of the fossil is almost exactly between 10 and 15 thousand years (y-axis), the ankle-bone length (x-axis) is at 240 nm. If you got a different answer, you may have been confused by the unusual alignment of the axes, as time is shown on the y-axis instead of the x-axis.

## 2.

The Correct Answer is (G) — To help you visualize and Predict, put your Pencil on Paper and extend the curve and axes. By 40,000 years ago, the ankle bone length would be around 310 mm long. (F) is incorrect because the ankle-bone length follows an increasing trend, and it was already at 290 mm around 35,000 years ago. (H) and (J) are incorrect even though they continue the upward trend, because the amount by which ankle-bone length increases is extremely high. It is unreasonable to expect the length to increase more than 40 mm in less than 5 thousand years, considering the fact that it took 25 thousand years for the previous increase of 40 mm from 250 mm to 290 mm.

## 3.

The Correct Answer is (A) — Each bar on the histogram represents an increase of 5 mm in the ankle-bone length. The first visible bar, which is exactly between the 220 mm and 230 mm marks on the graph, is the 225 mm bar you need to answer the question. If you chose (B), you may have thought that the leftmost bar represented lengths of 220 mm; however, the bar for 220 mm is not visible since there are not enough fossils. If you chose (C) or (D), you may have misread the labels on the y-axis.

## 4.

The Correct Answer is (H) — The question asks for the most frequently encountered ankle-bone width. To find this, you must first recognize that you need the most common ankle-bone length from Figure 2, and then refer to Figure 3 to identify the ankle-bone width which corresponds to it. The most common length (the tallest bar in Figure 2) is 240 mm. The only point on Figure 3 where the y-value is equal to 240 mm appears at approximately 32 mm on the H. hadarensis line. If you chose (F), (G) or (J), you may have incorrectly read one of the figures or confused the relationship between ankle-bone length and width.

## 5.

The Correct Answer is (B) — The question asks for the relationship of ankle-bone length with time, which points you toward Figure 1. The most recent data point is 10,000 years ago, when the ankle-bone length was 230 mm; the oldest data point is 35,000 years ago, when the bone length was 290 mm. This, along with the constant positive slope of the curve suggests that ankle-bone length has consistently decreased with time. If you chose (A), you may have misread the unusual axes of this graph, assuming that higher y-values meant more recent years. If you chose (D), you may have incorrectly referred to Figure 2.

## 6.

The Correct Answer is (G) — The question asks you to relate ankle-bone width to age, which means that you must first use Figure 3 to relate width to length, and then use Figure 1 to relate length to age. From Figure 3, the only ankle-bones with a width of 38 mm have a length of approximately 280 mm. Using Pencil on Paper to trace a line on Figure 1 from where the x-axis is equal to 280 mm gives you a point on the curve where the age is exactly 30 thousand radiocarbon years. If you chose (F), (H) or (J), you may have misread the axes or values on either one of the graphs, or confused the relationships between ankle-bone width, length and age.

## 7.

The Correct Answer is (A) — The question asks you to identify the protein with the highest concentration in the mouse and tick based on Figure 2. From the figure, you can see that the OspC has the highest concentration for both the tick (by a very large margin) and the mouse (by a smaller margin). You may have chosen (D) if you were looking for the proteins lowest concentration instead of the highest. You may have chosen (B) or (C) if you misread the information presented in Figure 2.

## 8.

The Correct Answer is (F) — The questions requires you to have read the second paragraph, in which it is outlined that the three proteins---one of which is Erp---are produced by B. burgdorferi in the hosts it infects. As such, without the bacteria inside of the tick, the concentration of all of the proteins will be incredibly low, if they are present at all. Referring to Figure 1, you can see that Stage 2 is the only stage where an uninfected tick is pictured. You may have chosen (J) if you thought the question was asking about mice. You may have chosen (G) or (H) if you missed part of the second paragraph that reveals that the three proteins are produced by the bacteria.

## 9.

The Correct Answer is (D) — The question asks you to refer to Figure 3 to find the point where their concentrations are equivalent; however, Figure 3 only shows the rates of production. You are required to recognize that the rate of production is directly related to the concentration. If two proteins are produced at the same rate, there will be equal amounts produced and equal concentrations. After identifying the correct curves based on the key, you can find that the intersection of the BpaB and OspC curves is between 30 and 35°C. If you chose (A), you may have been looking for the intersection of the BpaB and Erp curve. If you chose (B) or (C), you may have not have realized that the question requires you to find the intersection.

## 10.

The Correct Answer is (J) — The question asks you to find a temperature in Figure 3 that would directly correspond to the relationship between the concentrations of proteins in an infected tick. Figure 2 shows a very high concentration of OspC, and small concentrations of Erp and BpaB, in infected ticks. The only temperature range where the OspC curve is higher than both of the other curves is above 35°C. If you chose (F) or (G), you may have confused the Erp curve with the OspC curve. (H) may be tempting since the OspC curve is higher than the BpaB curve for a small portion, but you are looking for a point where the OspC curve is always higher than both of the other curves.

## 11.

The Correct Answer is (B) — The question asks you to determine, based on the text and Figure 3, whether the proteins surviving at 45°C will be enough for the survival of the bacteria. During your 3D Skim, you may have underlined the detail in Paragraph 2 which explains that the bacteria “requires all three proteins to survive in any host”. From Figure 3, you can see that only one of the proteins, OspC, will survive at this temperature. Therefore, you can conclude that the fever will kill B. burgdorferi. Using piecewise elimination, you can eliminate options (C) and (D). (A) is incorrect because the reason the bacteria will die is that Erp and BpaB are no longer produced, despite the fact that OspC continues to be produced. You may have chosen (C) if you misread the passage and thought that a single protein would be enough for the survival of the bacteria. You may have chosen (D) if you thought the question asked whether the bacteria would survive.

## 12.

The Correct Answer is (J) — The passage explicitly states in the first paragraph that the bacteria can only be carried by ticks and mammals---knowing that lizards are reptiles gives you the correct answer. If you chose (F) or (G), you may have missed the crucial detail in the first paragraph. If you chose (H), you might have forgotten that the proteins required for B. burgdorferi are produced at temperatures less than 25°C.

## 13.

The Correct Answer is (C) — The question asks you to identify the relationship between amount of salt and the freezing and boiling points of water. Moving down the table, you can see that as the mass of salt dissolved increases, the freezing point becomes more negative and the boiling point increases. Therefore, the freezing point decreases and boiling point increases. If you chose (A), you may have ignored the negative signs on the freezing points.

## 14.

The Correct Answer is (J) — The question asks you to identify the boiling point of water at a pressure of 1.05 atm. To see the relationship between boiling point and pressure, you must refer to Figure 2. You must find a point on the transition line between the liquid and gas phases at 1.05 atm on the figure. At the 1.00 atm mark, the temperature is already 100°C and increasing. Therefore, at 1.05 atm, the temperature will be greater than 100°C.

## 15.

The Correct Answer is (D) — The question asks you to extract from Figure 2 the conditions required for water to go from solid to gas directly. The region where the two phases (gas and solid) are directly adjacent is below 0.1°C and 0.01 atm. If you picked (A) or (B), you may have missed that phase change depends on both temperature and pressure, not on just one of the two. If you chose (C), you may have accidentally identified the region where the liquid and solid phases are adjacent.

## 16.

The Correct Answer is (G) — The question asks you to determine whether the temperature of water changes uniformly with respect to the energy added to it. If this were the case, Figure 1 would have to show a straight line with a constant slope. However, there are regions of the graph where the line becomes horizontal and the slope changes. Therefore, you can eliminate options (F) and (H), as they suggest that the slope is constant. (J) suggests that the temperature changes uniformly, but Figure 2 is not a straight line, so (J) is incorrect.

## 17.

The Correct Answer is (C) — The question asks you to predict the boiling point of water with 8 g of salt dissolved in it, which is 2 g more than the last data point shown on Table 1. Examining the difference between the boiling points on each row in Table 1, it can be seen that every 1 g increase in the mass of salt dissolved corresponds to an increase of 0.0089 °C in the boiling point. Therefore, 2 g of increase from the last data point would yield 100.0534 + (2 × 0.0089) = 100.0712°C. If you chose (B), you may have found the boiling point with only 7 g of salt. (A) and (D) are incorrect because they are too low and too high, respectively.

## 18.

The Correct Answer is (J) — The question asks you to find the freezing and boiling points for water at 10 atm of pressure based on Figure 2, and to identify the answer option with a corresponding figure. In Figure 2, the line between the liquid and solid regions intersects 10.00 atm exactly at -0.5°C, which is the freezing point. The line between the liquid and gas regions intersects 10.00 atm at 174°C, which is the boiling point. The only answer option that shows the phase changes at both these points is (J). If you chose (G) or (H), you may have neglected that the change in pressure affects both the boiling point and the freezing points. If you chose (F), you may have thought that the question was asking for the heating curve at 1.0 atm of pressure.