Researchers are investigating processes that happen during digestion. Which answer choice describes only a physical change during digestion?

The correct answer is B. Chewing in the mouth breaks food into small pieces.

Explanation:

In physical changes, substances do not change their chemical composition or properties but only physical features such as this. This occurs during the chewing because the action of chewing only makes food to be broken down in smaller pieces but does not change its identity, composition, or properties. This does not occur once the food is in contact with saliva, the acid in the stomach, etc. because in these cases, the food reacts with other substances and a chemical reaction occurs, which changes food's identity and composition.