As U.S. nuclear attack submarines prowl their familiar haunts deep within the oceans of the world these days, they increasingly are engaged in missions far different from the tasks for which they were built
and for which their crews were trained over the last forty years.
Although the meaning of this sentence can be easily understood, it is important to heed the placement of increasingly. “They increasingly are engaged in…” suggests that the frequency in engaging in missions far different from the original tasks of these submarines has gone up. So we need to keep this meaning intact in the original choice.
• This sentence does not have any SV agreement error.
• All the verbs are used in correct tense.
• Pronoun “they” correctly refers to “US nuclear attack submarines”.
• Adverb “increasingly” correctly modifies the verb “engage”.
• The parallelism is also maintained in the sentence – “for which they were built” and “for which their crews were trained over the last forty years.
• The sentence uses the correct idiom “different from”.
So this sentence is correct as is.
Let us now eliminate the wrong answer choices on solid grounds through the POE
they increasingly are engaged in missions far different from the tasks for which they were built. Correct
for reasons stated above.Choice B:
the missions they increasingly engage in are far different than the tasks they were built for:Incorrect
• Firstly, there is a very slight meaning chance when we change the passive “they increasingly are engaged” to active “they increasingly engage”. When written in active, the sentence suggests that the doer is consciously engaging in some activity. However, when written in passive, the sentence does not suggest this conscious effort. It rather suggests that the doer is asked to do that activity.
• Secondly, use of “different than” is not correct in this context. In GMAT, “different from” is preferred over “different than”. Also “different than” should be followed a clause and not only a noun.Choice C:
they engage increasingly in missions that differ significantly from the tasks they were built for: Incorrect
• With the change in place of “increasingly”, it somehow now denotes not the frequency but the degree of engagement of these submarines into missions different from their original tasks.
• This choice has parallelism issue. “they were built for” is not parallel to “for which their crews were trained…”.Choice D:
the missions they engage in are increasingly different than the tasks for which they were built: Incorrect
• Same active voice implication as in choices B and C.
• “increasingly” now modifies different, meaning that missions are now increasingly different rather than the submarines increasingly engaging in these missions.Choice E:
they increasingly engage in missions far different than the tasks for which they were built: Incorrect
because of implication of active voice and the idiom “different than”.
Hope this helps.