The protein molecule must be digested before it can be transported to and utilized by the cells because (a) protein is only useful directly, (b) protein has a low pH, (c) proteins in the circulating...

The protein molecule must be digested before it can be transported to and utilized by the cells because

(a) protein is only useful directly,

(b) protein has a low pH,

(c) proteins in the circulating blood produce an adverse osmotic pressure,

(d) the protein is too large to be readily absorbed.