試題詳解

59.Cows are able to survive on a diet consisting almost entirely of cellulose because
(A) cows are autotrophic;
(B) cows can manufacture all 20 amino acids out of sugars in the liver;
(C) unlike humans, the saliva the cow produces has enzymes capable of digesting cellulose;
(D) cows have cellulose-digesting, symbiotic microorganisms in their rumens.