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A Choice (A) is correct because it matches the passage, which states that Iceland was created
by lava flow that bubbled up from between two tectonic plates at a mid-ocean ridge.
Choice (B) contrasts an island and a continent, which the passage does not, while (C) states
that the author mentions Iceland to prove that an island can be a volcano. The author never
says that an island can’t be a volcano, so (C) is incorrect. Choice (D) is true, but it doesn’t
answer the question. Iceland does straddle the mid-Atlantic ridge, but the reason that the
author mentions Iceland is to give an example of an island that was created by lava flow at
a hot spot.

D The passage says that the lava flows more abundantly in certain spots, producing
volcanic islands (lines 70–72) and underlie the large, highly volcanic island of Iceland,
which straddles the Mid-Atlantic Ridge (lines 75–76). Thus, (D) is correct. Choices (A),
(B), and (C) do not coordinate with any answer choices in the previous questions.

A The author uses the phrase Some geologists propose to show that plate tectonics are a
theory, and there are still things about it that scientists don’t know and want to learn. Thus,
(A) is correct. The passage never mentions a lack of data, so (B) can be eliminated, while
(C) implies that the phrase is introducing an opposing viewpoint, which it does not. Choice
(D) refers to the continental-drift theory, which is not part of the logic of this paragraph, so
it is incorrect.

B The passages states that plumes of molten rock, often called hot spots, rise and erupt
through the crust of a moving plate. The diagram depicts this process with a line traveling
up through the lithosphere to the surface. Therefore, (B) is correct. While the diagram does
depict a continental rift zone by the ocean, there is no evidence in the graph or the passage
that this is always the case. Therefore, (A) is incorrect. The passage states that mid-ocean
ridges mark boundaries where plates are forced apart as new ocean floor is being
created between them; thus, (C) can be eliminated. There is no mention in either the
passage or the diagram of the relative rigidity of oceanic and continental crust, so (D) can
be eliminated as well.

B The author’s main point in the first paragraph is that the construction of the Glen Canyon
Dam did affect downstream resources, including the loss of large beaches used for
camping and the addition of several animals to the endangered species list. Choice (B)
matches the context of this passage, so keep it. Eliminate (A), as no mention is made of
maintaining water resources. According to the passage, the fish were adapted to the pre-
dam era, so (C) doesn’t work because decimated is too extreme. Choice (D) is the opposite
of what the first paragraph suggests, so eliminate it. Choice (B) is the answer.

A The correct answer to the previous question was that the dam was built with a lack of
foresight. This is shown best with (A), since it’s mentioned that little consideration was
given to how dam operations might affect downstream resources. Choices (B) and (D)
both show consequences but don’t necessarily match the phrase little consideration, so
eliminate them. Choice (C) isn’t negative at all, so get rid of it. The correct answer is (A).

A The passage states that the scientists and recreationists observed the physical