Incorrect.
Go through the numbers and you'll find un-prime numbers ending in 1:
21, 81, 121,...
The <u><em>correct answer</em></u> is:
d) People per hour, because the dependent quantity is the people
Explanation:
In this situation, the two quantities are people and hours. These are the two things in this problem we can count or measure.
The independent variable is the one that causes a change, while the dependent variable is the one that <em>gets</em> changed. In this situation, the number of people change every hour; this means the number of people <em>gets</em> changed, which makes it the dependent variable. This means that the independent variable must be time.
Since people is dependent and time is independent, "people per hour" would be the best form of this statement.
