The Relationship Between the Standard Normal Random Variable Z and Normal

The relationship between the standard normal random variable z and normal random variable X is that:

A) Only the normal random variable X is continuous.
B) Only the standard normal variable z is continuous.
C) The standard normal variable z counts the number of standard deviations that the value of the normal random variable X is away from its mean.
D) The values of the standard normal random variable z cannot be negative.
E) The values of the normal random variable X cannot be negative.