Which is NOT true about probability density functions? 

A. The total area under the curve of a probability density function and above the horizontal axis is 1. 

B. Using a probability density function to compute the probability of a single value occurring (such as the probability that someone’s weight is exactly 164 pounds) will result in zero. 

C. Normal distributions are examples of probability density functions. 

D. Probability density functions may extend indefinitely to negative or positive infinity. 

E. All probability density functions are bell-shaped.