Cow proteins and human proteins are different, so how can people use cow proteins when they eat beef?

A. Cow proteins are broken down into atoms, which then can be used to build human proteins.

B. Cow proteins can be used by the human body after the body alters them slightly.

C. Cow proteins are only slightly different from human proteins, so they can be used directly by the human body.

D. Cow proteins are broken down into smaller molecules, which then can be used to build human proteins.