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!
