Why Are Cattle Able to Survive on a Diet Consisting

Why are cattle able to survive on a diet consisting almost entirely of plant material?

A) They are autotrophic.
B) Cattle, like the rabbit, reingest their feces.
C) They manufacture all 15 amino acids out of sugars in the liver.
D) Cattle saliva has enzymes capable of digesting cellulose.
E) They have cellulose-digesting, symbiotic microorganisms in chambers of their stomachs.