The correct option is A P(A′B′)=[1−P(A)][1−P(B)]
Two events A and B are said to be independent, if P(AB)=P(A)×P(B)
Consider the result given in alternative B.
P(A′B′)=[1−P(A)][1−P(B)]
⇒P(A′∩B′)=1−P(A)−P(B)+P(A)⋅P(B)
⇒1−P(A∪B)=1−P(A)−P(B)+P(A)⋅P(B)
⇒P(A∪B)=P(A)+P(B)−P(A)⋅P(B)
⇒P(A)+P(B)−P(AB)=P(A)+P(B)−P(A)⋅P(B)
⇒P(AB)=P(A)⋅P(B)
This implies that A and B are independent, if P(A′B′)=[1−P(A)][1−P(B)]