submirines

[rashel]

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.
(A) they increasingly are engaged in missions far different from the tasks for which they were built
(B) the missions they increasingly engage in are far different than the tasks they were built for
(C) they engage increasingly in missions that differ significantly from the tasks they were built for
(D) the missions they engage in are increasingly different than the tasks for which they were built
(E) they increasingly engage in missions far different than the tasks for which they were built

[Shooter]

I'll take A.

'different from' not 'different than'.
Discard B,D,E.
Between A and C, A is parllel.

for which they were built and for which their crews were trained.

[Rising_Sun]

One more vote for A.

[sushkan2008]

Yes A for me too...

[mitzi]

My pick is A.

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.

(A) they increasingly are engaged in missions far different from the tasks for which they were built
1) "they" refer to plural subject, U.S. nuclear attack submarines, in subordinate clause
2) idiom : "engaged in" and "different from" . please note that different than is wrong.
3) passive voice : "they were built" and "their crews were trained" are parallel.

[Roland]

Will go with A too. Built for isnt parallel so eliminates B and C. Inital modifying clause is supported by "they increasingly are". Leaves us with A and E. Since idiom "different from" hence A.

[aseemrules]

A for me tooo