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7. Displays of the aurora borealis, or "northern lights," can heat the atmosphere over the arctic enough to affect the trajectories of ballistic missiles, induce electric currents that can cause blackouts in some areas and corrosion in north-south pipelines.

(A) to affect the trajectories of ballistic missiles, induce

(B) that the trajectories of ballistic missiles are affected, induce

(C) that it affects the trajectories of ballistic missiles, induces

(D) that the trajectories of ballistic missiles are affected and induces

(E) to affect the trajectories of ballistic missiles and induce

8. The golden crab of the Gulf of Mexico has not been fished commercially in great numbers, primarily on account of living at great depths-- 2,500 to 3,000 feet down.

(A) on account of living

(B) on account of their living

(C) because it lives

(D) because of living

(E) being they live

Answer

7．The use of the phrasing can heat... enough to affect in A and E is more idiomatic than the use of the subordinate clause beginning with that in B, C, and D. Also, B produces an illogical and ungrammatical statement by making induce parallel with the verb heat rather than with the appropriate form of the verb affect;

C lacks agreement in using the singular pronoun it to refer to the plural noun displays; and D is faulty because induces cannot fit grammatically with any noun in the sentence. Choice A incorrectly separates the two infinitives to affect and [to] induce with a comma when it should compound them with and, as does E, the best choice.

8．As used in choices A, B, and D, the phrases on account of and because of are unidiomatic; because, which appears in C and E, is preferable here since because can introduce a complete subordinate clause explaining the reason why the golden crab has not been fished extensively. B and E also produce agreement errors by using the plural pronouns their and they to refer to the singular noun crab. Choice D, like A, fails to provide a noun or pronoun to perform the action of living, but even with its the phrases would be more awkward and less clear than it lives. C, which uses because and it as the singular subject of a clause, is the best choice.

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