Stimulants, such as caffeine, can eliminate pain and fatigue and enhance alertness, but, if used continuously for long periods, can cause users to develop tolerance and even addiction.
a)pain and fatigue and enhance alertness, but, if used continuously for long periods, can cause users to develop tolerance and even addiction
b)pain, fatigue, and enhanced alertness; if used continuously for long periods, though, users can develop tolerance and even addiction to them
c)pain, fatigue, and enhance alertness; people having used them continuously for long periods, though, can develop tolerance and even addiction to them
d)pain and fatigue while enhancing alertness, but, if used continuously for long periods, users can develop tolerance and even addiction to them
e)pain and fatigue, and also enhancing alertness; however, people using them continuously for long periods can develop tolerance and even addiction
The official answer given for this question is A) . Here are my 3 questions related to the correct choice A) and the choice D) that I selected.
1. Although punctuations are not tested in the GMAT, shouldn't there be a COMMA after "pain and fatigue" in the option A) ?
2. The explanation given for why D) is not correct is "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." . My question is if statements in general doesn't modify nouns and thus, can we not assume that the subject is implied in this i.e "if <stimulants are> used continuously for long periods" and therefore the if statement doesn't need to modify the noun "users".
3. Is this construction "cause users to develop" not redundant in A) ?