Lecture 8 (Logic) Interchanging Quantifiers and Introducing Identity

Which pair of formulas is NOT logically equivalent?

1. A.∀x P(x) and ¬∃x ¬P(x)
2. B.∃x P(x) and ¬∀x ¬P(x)
3. C.¬∀x P(x) and ∃x ¬P(x)
4. D.∀x∃y P(x,y) and ∃y∀x P(x,y)