问题
单项选择题
A joint probability of A and B must always be:（）
A. less than or equal to the conditional probability of A given B.
B. greater than or equal to the conditional probability of A given B.
C. greater than or equal to than the probability of A or B.
答案
参考答案：A
解析：
By the formula for joint probability: P(AB)=P(A|B)×P(B), since P(B)≤1, then P(AB)≤P(A|B). None of the other choices must hold.