12 . J According to Figure 3, the marine deposition of SO 4 2− was not studied, eliminating (F). The
marine deposition of Mg2+ changed during the study, eliminate (G). According to Figure 1,
the movement of water during the month changed every month during the twelve-month
period, eliminating (H). Only the location of the study, the Atlantic Ocean, was held constant,
making (J) the correct answer. The location of the study was not changed until Study 3.
Passage III
13 . B We’re dealing with Figure 2, which shows the data for the canopy layer. The question asks
about the leaf area index, so we need the solid line and the y-axis shown on the left side of
the figure. Once all those elements are in place, you find that the leaf area index in Year 14
was closest to 1.3. Make sure you are dealing with the correct figure and the correct axes
given on that figure.
14 . F Table 1 shows a direct relationship: As precipitation goes up, leaf-area index goes up.
Therefore, we can expect the leaf-area index at 1.70 mm/km^2 /yr of precipitation to be below
the leaf-area index at 1.80 mm/km^2 /yr. The leaf-area index at 1.80 mm/km^2 /yr is 5.2, and the
only answer choice that gives a value in between is (F).
15 . A This problem asks about the canopy layer and the understory layer, so we will need to use
Figures 2 and 3. Take a look at these two graphs: The two curves in the canopy-layer graph
seem to go up and down at roughly the same rate, whereas the two curves in the understory-
layer graph don’t seem to have a consistent relationship. Because the canopy-layer graph
shows a more consistent relationship, we can eliminate (B) and (D). A more consistent
canopy-layer graph also disagrees with the botanist’s statement from the problem,
eliminating (C). Only (A) contains the correct answer to the question and the correct reason
for that answer.
16 . G Use Figures 1, 2, and 3 to determine each of the annual precipitation values in Year 7. This is
the dotted curve, and the values are on the y-axis on the right side of each figure. For the
emergent layer shown in Figure 1, the annual precipitation was roughly 1.33. For the canopy
layer shown in Figure 2, the annual precipitation was roughly 1.0. For the understory layer
shown in Figure 3, the annual precipitation was roughly 0.67. You don’t need to worry about
exact figures: emergent should be the largest and understory should be the smallest. Only
(G) works.
17 . D Use POE. All the answers use values of meters above the rainforest, but meters is not a
variable on any figure. A quick scan of the introduction for those values identifies “0–30” as
the understory layer, “30–45” as the canopy layer, and “45–55” as the emergent layer.
