Answer the following question given this paragraph: 

The esophagus is a narrow tube that carries food from the throat to the stomach. Food moves through the esophagus because of peristalsis. At the lower end of the esophagus, a circular muscle controls the opening to the stomach. The muscle relaxes to let food pass into the stomach. Then the muscle contracts again to prevent food from passing back into the esophagus.


Q: What causes food to move through the esophagus?

 Choices:

- photosynthesis

- proteolysis

- apoptosis

- peristalsis

A:
peristalsis
