Which of the Following Most Likely Represents a Discrete Random

Multiple Choice

Which of the following most likely represents a discrete random variable?

A) Length of time between calls to an 800 number.
B) The number of years completed in the military services.
C) The S & P Industrial average of stock prices.
D) The amount of retail sales on a given day.
E) Length of time for which an apartment in a large complex remains vacant.