Event a occurs with probability 0.2. event b occurs with probability 0.8. if a and b are disjoint (mutually exclusive), then

a) p(a and b) = 0.16
b) p(a or b) = 1.0
c) p(a and b) = 1.0
d) p(a or b) = 0.16

B.

Step-by-step explanation:

If A and B are disjoint events, then P(A∩B) = 0 (because A and B haven't common parts), intersection ∩ can be also denoted with "and", so P(A and B) =0.

On the other hand, if A and B are disjoint events, then P(AUB) = P(A)+P(B). Union U can be also denoted with "or", then P(A or B) = P(A)+P(B).

P(A or B)= 0.2+0.8 = 1.

So, the answer is B.