The time on homework is the independent variable, the correct option is D.
Given
Brenda conducts a survey of 100 students to see how their study habits and their grades are related.
She wants to see whether students who spend more time on homework have higher grades.
An independent variable is a variable that does not depend on any other variable for its value.
Hence, the time on homework is the independent variable.
To know more about independent variables click the link given below.
https://brainly.com/question/967776