The marines who landed on the beaches of Iwo Jima effected the rescue of several prisoners of war whose assault took the enemy by surprise.(A) The marines who landed on the beaches at Iwo Jima effected the rescue of several prisoners of war whose assault took the enemy by surprise.
(B) The marines effected the rescue of several prisoners of war who had landed on the beaches at Iwo Jima and whose assault had taken the enemy by surprise.
(C) The marines who landed on the beaches at Iwo Jima effected the rescue of several prisoners of war whose assault had taken the enemy by surprise.
(D) The marines who landed on the beaches at Iwo Jima affected the rescue of several prisoners of war whose assault had taken the enemy by surprise.
(E) The marines who landed on the beaches at Iwo Jima, and whose assault took the enemy by surprise, effected the rescue of several prisoners of war.
Source: Master GMAT
I chose E.
A: POW's did the result? No. This changes the meaning of the sentence
C: Same reasoning as B.
D: Wrong use of 'Affect'. You want to use 'Effect' when explaining an end result. You use 'Affect' when describing an action.