Final Answer:
The variable that is NOT a discrete variable among the options is b. Average temperature across counties in Arizona.
Step-by-step explanation:
Discrete variables are those that can only take distinct, separate values, usually counted in whole numbers. Options a, c, and d involve counts or specific values:
a. Review out of 5 stars for service at the DMV: This is discrete, as it can only take values like 1, 2, 3, 4, or 5.
c. Number of heads in five coin flips: This is discrete, as it involves counting the number of heads, which can only be a whole number.
d. Number of moons around a planet: This is discrete, as the count of moons is a whole number.
However, option b. Average temperature across counties in Arizona: is a continuous variable, as temperature can take any value within a range, including decimals, and is not restricted to distinct, separate values.
Option B is the answer.