As P(A) and P(B) are mutually exclusive event.

∴ P(A ∪ B) = P(A) + P(B)

As P(A ∪ B) ≤ 1

∴ P(A) + P(B) ≤ 1

⇒ P(A) ≤ 1 – P(B)

⇒ P(A) ≤ P(B’)

Our answer matches with option (a)

∴ Option (a) is the only correct choice