B怎么错了，感觉说法差不多？是因为有正态分布的差别吗？

问题如下：

Which of the following most accurately describes how to standardize a random variable X?

选项：

A.Subtract the mean of X from X, and then divide that result by the standard deviation of X. B.Subtract the mean of X from X, and then divide that result by the standard deviation of the standard normal distribution. C.Divide X by the difference between the standard deviation of X and the standard deviation of the standard normal distribution.

解释：

There are two steps in standardizing a random variable X: Subtract the mean of X from X, and then divide that result by the standard deviation of X. This is represented by the following formula: Z = (X – μ)/σ.