AP BIOLOGY

Detailed explanation-1: -Impossible event is an event that is non existing. There is no possibility that it can happen. Hence the probability of occurrence is 0.

Detailed explanation-2: -The probability of an impossible event is always 0.

Detailed explanation-3: -Therefore the probability of an impossible event is zero.

Detailed explanation-4: -Empty events are always considered as impossible. Notice that an empty event is both empty and has probability zero. That is because it is described by the empty k-event which has zero probability by definition. Thus, empty events are impossible because they are empty and because they have zero probability.