In the mid-1960's a newly installed radar warning system

[BTGmoderatorDC]

In the mid-1960's a newly installed radar warning system mistook the rising of the moon as a massive missile attack by the Soviets.

(A) rising of the moon as a massive missile attack by the Soviets

(B) rising of the moon for a massive Soviet missile attack

(C) moon rising to a massive missile attack by the Soviets

(D) moon as it was rising for a massive Soviet missile attack

(E) rise of the moon as a massive Soviet missile attack

OA B

Source: Official Guide

[Brent@GMATPrepNow]

In the mid-1960's a newly installed radar warning system mistook the rising of the moon as a massive missile attack by the Soviets.

(A) rising of the moon as a massive missile attack by the Soviets

(B) rising of the moon for a massive Soviet missile attack

(C) moon rising to a massive missile attack by the Soviets

(D) moon as it was rising for a massive Soviet missile attack

(E) rise of the moon as a massive Soviet missile attack

OA B

Source: Official Guide

The idiom here is "Mistake x FOR y"

So, we can eliminate A, C and E
We're left with B and D

D conveys an ambiguous message, because it suggests that the moon was rising for an attack.
ELIMINATE D

Answer: B

Cheers,
Brent