A student is eating a meat and cheese taco for lunch. After taking a bite he chews his taco into smaller pieces. Then enzymes in the saliva start to break down the carbohydrates in the tacos into simple sugars. Which part of the digestive process best describes a chemical change from the passage above?

Chewing the taco into smaller pieces.

Enzymes in the saliva breaking down carbohydrates into simple sugars

The tongue pushing the taco down his throat.

Swallowing his food down the esophagus