Question

Why is it possible to swallow while standing on one's hands?

1. Valves in the digestive system keep food from moving backward.
2. Peristalsis pushes food along the digestive tract in the right direction.
3. Bacteria clog the digestive tube and prevent food from moving in the wrong direction.
4. A wave of muscle contractions called emulsification prevents food from moving backward.

Answer 1

Peristalsis pushes food along the digestive tract in the right direction.