A student conducts an experiment to test how music affects plant growth. In the experiment, she uses two identical plant seedlings. One plant is exposed to classical music. The other plant is exposed to no music. She measures and compares the different plants' height each week, for two months of time.

What is the independent variable in this experiment?

A. two months of time
B. height of the plants
C. type of plant seedlings
D. exposure to music

How does the digestive system interact with the circulatory system? a. messages sent as electrical impulses from the digestive system are transported throughout the body by the circulatory system. b. nutrients taken in and broken down by the digestive system are carried to various parts of the body by the circulatory system. c. nutrients and gases are absorbed by organs in the circulatory system. then, they are transported to all parts of the body by organs in the digestive system. d. oxygen and carbon dioxide are exchanged by organs in the digestive system, and the gases are carried to the rest of the body by the circulatory system.