Final answer:
Food is propelled through the esophagus to the stomach by peristalsis, which are involuntary wave-like muscle contractions that ensure one-way movement of the food bolus.
Step-by-step explanation:
Food moves through the esophagus to the stomach via a process called peristalsis. This is a series of wave-like muscle contractions that propel the food forward. The chewed and moistened food, known as a bolus, enters the esophagus upon swallowing, where sequential squeezing of the esophageal muscles pushes it towards the stomach. This involuntary action ensures food moves in only one direction, from the mouth to the stomach, with reverse movement typically occurring only during vomiting.
The correct answer to the student's question is: a) Peristalsis. Additionally, when referencing what process occurs throughout most of the alimentary canal, the correct answer is b) propulsion, which includes the action of peristalsis that moves food and waste through the entire digestive tract.