The Plant Alkaloid Ricin Is Nontoxic Inside Castor Beans,but Becomes

The plant alkaloid ricin is nontoxic inside castor beans,but becomes active when digested by an animal.The toxic form of ricin kills by

A) inactivating the animal's immune system.
B) over stimulating the animal's heart rate.
C) inactivating ribosomes needed for translation.
D) binding to RNA polymerase.
E) releasing cyanidE.