TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: The correct order of food traveling through the digestive system after it is swallowed is: esophagus, stomach, small intestine, large intestine.

SOLUTION: Which list gives the correct order of food traveling through the digestive system after it is swallowed?

PROBLEM: When an atom gains or loses an electron it becames a(n) ion.

SOLUTION: When an atom gains or loses an electron it becames an?

PROBLEM: The energy content of foods is often expressed in calories.

SOLUTION:
Energy contents of foods are often expressed in what?