单选题

By definition, the probability of any event, E, is a number between:

A、 zero and positive one.
B、 zero and positive infinity.
C、 minus one and positive one.

【正确答案】 A

【答案解析】

A is correct. The two defining properties of a probability are as follows:
1) The probability of any event, E, is a number between 0 and 1.
2) The sum of the probabilities of any set of mutually exclusive and exhaustive events equals 1.