Question

a student is investigating horsepower in trucks. she proposes the following question: how does amount of horsepower affect the pulling ability of the truck? what is the independent variable?
the amount of horsepowers
the brand of the truck
changing speeds of trucks
pulling capability of the truck

Explanation:

The independent variable is the factor that is changed or controlled in an experiment to test its effect on the dependent variable. Here, the student is testing how horsepower affects pulling ability, so horsepower is being manipulated.

Answer:

A. the amount of horsepowers