The primary functions of epithelium include:

A. To protect the tissues that lie beneath from radiation, desiccation, toxins, invasion by pathogens, and physical trauma
B. The regulation and exchange of chemicals between the underlying tissues and a body cavity
C. The secretion of hormones into the circulatory system, as well as the secretion of sweat, mucus, enzymes, and other products that are delivered by ducts
D. To provide sensation
E. Absorb water and digested food in the lining of digestive canal.