If R is not reduced, which one of the following must be true?

Lizzie on July 31, 2019

Why not B?

Why is the correct answer not B?

Reply

Ravi on August 1, 2019

@Lizzie-Annerino,

Let's take a look at (B) and (A).

If R is not reduced, then we know that L and M must both be reduced.

If L is reduced, then we know that P is not reduced. This means that P
and R occupy 2 of the 3 "not reduced" slots.

Recall the rule that states if N is reduced, neither R nor S is
reduced. We know that R isn't reduced, so the necessary condition for
that part of the rule is satisfied. However, look at the rest of the
rule. If N is reduced, then S can't be reduced. Conversely, if S is
reduced, then N can't be reduced. This means that either N or S can't
be reduced.

From this, we know that both W and G must be reduced.

(A) says G is reduced, and we know that must be true, so it's the
correct answer choice.

(B) says that N is not reduced. It's possible that N is reduced,
however. We just know that either N or S is not reduced, but it's
possible that N is the one that's reduced and S isn't reduced, so we
can get rid of (B).

Does this make sense? Let us know if you have any other questions!