Which statements best describe mechanical digestion? Select all that apply.

A: Mechanical digestion breaks large food particles down into smaller ones. B: Chemical digestion involves the breaking of covalent chemical bonds in organic molecules by digestive enzymes. C: Absorption begins in the stomach, where some small, lipid-soluble molecules, such as alcohol and aspirin, can diffuse through the stomach epithelium into the circulation. D: Transport requires carrier molecules and includes facilitated diffusion, cotransport, and active transport.