Astronauts in Zero Gravity Are Able to Move Food Through

Astronauts in zero gravity are able to move food through their digestive tracts because

A) smooth muscle produces waves of contractions that propel material through the digestive tract.
B) skeletal muscle puts pressure on the digestive tract.
C) cardiac muscle maintains a high pressure that moves material through the digestive tract.
D) striated muscle creates a pressure gradient that forces material from one end of the digestive tract to the other.
E) skeletal muscle sphincters contract and allow materials to move through digestive tract.