Stimulants, such as caffeine, can eliminate pain and fatigue and enhan

here is OE

The sentence juxtaposes certain positive and negative effects of stimulants. There are two positive effects cited—(a) the elimination of pain and fatigue, and (b) the enhancement of alertness. On the other hand, negative effects—the development of tolerance and/or addiction—are also cited.

The two positive effects should appear in a parallel structure. The sentence should also use a proper transition to express the contrast between the positive and negative effects. Finally, the sentence must use modifiers accurately; specifically, “if used continuously…” must properly refer to the stimulants themselves, not to their users.

(A) CORRECT. This choice may at first appear to have an unusual structure—specifically, it may appear to be of the form x or y or z—but, on closer inspection, that’s not the construction at work here. Instead, this choice properly places two positive effects of stimulants—eliminate pain and fatigue and enhance alertness—in parallel. The first “and” connects pain and fatigue within the first of the two parallel structures, while the second “and” connects the two parallel structures themselves; therefore, both instances of “and” are necessary.

The modifier if used… properly refers to the subject of the clause, i.e., stimulants. Finally, can cause… is the second half of a compound verb (can eliminate… but… can cause…), whose subject is stimulants as required by context.

(B) In this choice, pain, fatigue, and enhanced alertness are all placed in parallel. This construction is nonsense, as it suggests that stimulants can eliminate all three of these phenomena. (In context, it is clear that stimulants produce, rather than eliminate, enhanced alertness.) Additionally, the modifier if used continuously for long periods… illogically describes the subject of the following clause, which is users. In context, that modifier should describe stimulants, not users.

(C) The nouns pain and fatigue are not parallel to the verb enhance. Additionally, the modifier having used… is illogical here. It is the process of using the stimulants themselves—not the retrospective fact of having used them—that leads to tolerance or addiction.

(D) The modifier if used continuously for long periods… illogically describes the subject of the following clause, which is users. In context, that modifier should describe stimulants, not users.

(E) Eliminate and enhancing are not parallel.

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