U.S. nuclear attack

[vaibhav.iit2002]

142. 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

Plz provide reasoning for A and C

[xcusemeplz2009]

142. 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 increasingly has to modify the verb engage
(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

Plz provide reasoning for A and C

[nervesofsteel]

(A) they increasingly are engaged in missions far different from the tasks for which they were built<- IMO Correct as increasingly and far are modifying engaged and different...

(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<- I think significantly differ and increasingly engage should be the correct usage..

(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

[Ludacrispat26]

Just to confirm, is "different than" incorrect in GMAT English, whereas "different from" is correct?

[vaibhav.iit2002]

(A) they increasingly are engaged in missions far different from the tasks for which they were built<- IMO Correct as increasingly and far are modifying engaged and different...

(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<- I think significantly differ and increasingly engage should be the correct usage..

(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

Oh Thanks !!
I missed the idiom. You are right.

[nervesofsteel]

Whts the OA...??

[gmatv09]

IMO A...