In refer to the given values, then identify which of the following is most appropriate: discrete random variable, continuous random variable, or not a random variable.

a. Exact weights of the next 100 babies born in the United States
b. Responses to the survey question “Which political party do you prefer?”
c. Numbers of spins of roulette wheels required to get the number 7
d. Exact foot lengths of humans
e. Shoe sizes (such as 8 or 8½) of humans