Diya wants to test the effect of listening to different types of music on the human heart rate. She takes the resting heart rate of her test subjects then has them listen to one type of music for 5 minutes and takes their heart rate again. Each test subject repeats the test listening to three different types of music.
What is the independent variable in Diya’s experiment?
A. Listening for 5 minutes
B. Effect of listening
C. Different types of music
D.Heart rate