Correct Answer - Option 2 : y alone

1) P is equal to or not shorter than Q.

⇒ P ≥ Q

2) N is as tall as P.

⇒ N = P ≥ Q

3) M is taller than or equal to N.

⇒ M ≥ N = P ≥ Q

Conclusions:

(x) M is taller than P → False (M ≥ N = P → M ≥ P)

(y) N is equal to or taller than Q → True (N = P ≥ Q → N ≥ Q)

Hence, option 2 is the correct answer.