the addition of acids to create a ball of food the secretion of pepsin to change proteins to peptides the breakdown of food substances by digestive juices the squeezing of food through the intestines
I gave my students this multiple choice question: Which of these indicates a physical change that occurs during the process of digestion?

Only one answer is correct among these 4 choices:
- the addition of acids to create a ball of food
- the secretion of pepsin to change proteins to peptides
- the breakdown of food substances by digestive juices
- the squeezing of food through the intestines

Could you tell me which one is correct?

the squeezing of food through the intestines