问题
单项选择题
Let A and B be two mutually exclusive events with P(A) =0.40 and P(B)=0.20. Therefore :（）
A. P(B|A)=0.20.
B. P(A and B)=0.
C. P(A or B)=0.52.
答案
参考答案：B
解析：
If the two evens are mutually exclusive, the probability of both ocurring is zero.