Context: The passage below describes an experiment. Read the passage and think about the variables that are described.

Audrey was building a wooden race car. She could choose between two types of wheels for the car. Each of these wheels was ten inches in diameter, but one type was heavier than the other. Audrey was curious if the weight of the wheels would affect how fast her race car could go down the race hill.
Audrey put the lighter set of wheels on the car and rolled down the hill three times. She measured how long it took her to get to the bottom each time. Then, she put the heavier set of wheels on the car and rolled down the hill three more times. Once again, she measured how long it took to reach the bottom of the hill each time.
Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.
Figure: wooden race cars.
Which of the following was an independent variable in this experiment?
A. the amount of time it took to reach the bottom of the hill
B. the weight of the wheels
Choose the right answer from the options and respond with its letter.

B