Which of the following is always true for all probability density functions of continuous random variables?
A. They are bell-shaped
B. They have the same height
C. The area under the curve is 1.0
D. They are symmetrical

A standard normal distribution is a normal distribution with
A. a mean of zero and a standard deviation of one
B. a mean always larger than the standard deviation
C. a mean of one and a standard deviation of zero
D. a mean usually larger than the standard deviation