问题
单项选择题
If X and Y are independent events, which of the following must be TRUE（）
A. P( X or Y)=P(X)+P(Y).
B. X and Y cannot occur together.
C. P(X|Y)=P(X).
答案
参考答案：C
解析：
Note that events being independent means that they have no influence on each other. It does not necessarily mean that they are mutually exclusive. Accordingly, P(X or Y)=P(X)+P(Y)-P(X and Y). By the definition of independent events, P(X|Y)=P(X).
