Question

lactase is a protein in the digestive tract that helps break down certain sugars found in milk. what is the main function of lactase?

to provide structure
to fight disease
to maintain homeostasis
to regulate cell reactions

Explanation:

Lactase is an enzyme. Enzymes are proteins that act as biological catalysts to regulate (speed up) chemical reactions in cells. Breaking down sugars (a chemical reaction) in the digestive tract aligns with regulating cell reactions. Proteins that provide structure are like structural proteins in muscles etc. Proteins that fight disease are antibodies. Maintaining homeostasis is a broader function that many body systems contribute to, and lactase's specific role is more about reaction regulation.

Answer:

to regulate cell reactions