Both the esophagus and the small intestine are involved in the digestion of food. The esophagus squeezes food into the stomach by wave-like muscle contractions. Peptidase enzymes in the small intestine break food molecules into smaller molecules. Which statement best describes changes to food during digestion?

A. The muscle contractions and the action in the peptidase both result only in chemical changes.

B. The muscle contractions and the action of the peptidase both result only in physical changes.

C. The muscle contractions result in physical changes, while the action of the peptidase results in chemical changes.

D. The muscle contractions result in chemical changes, while the peptidase results in physical changes.

Which statements best describe the differences or similarities between a comparative investigation and an experimental investigation? check all that apply. experimental investigations are best for showing cause-and-effect relationships, while comparative investigations do not necessarily show this type of relationship. comparative investigations are often impractical and unrealistic, while experimental investigations are the most practical and realistic kinds of investigations. comparative investigations allow for the use of a wide range of variables but do not have a control group, while experimental investigations involve variables that can be controlled. both experimental investigations and comparative investigations are designed to answer scientific questions. both experimental investigations and comparative investigations focus on making observations rather than collecting new data.