NO.PZ2018062016000079
问题如下：
Given that x is a discrete random variable, the corresponding cumulative probability function is F(x), which of the following is least correct？
选项：
A.
0 ≤ F(x) ≤ 1
B.
∑F(x)=1
C.
F(x)=P(X≤ x)
解释：
B is correct. Based on the definition of cumulative probability function, F(x)=P(X≤ x) and 0 ≤ F(x) ≤ 1 always holds because 0 ≤ p(x) ≤ 1.
看提问里说B是错的，但是我选的C，说B是正确答案，搞糊涂了
