Essayist: When the first prehistoric migrations of humans

(A) Animals weakened by disease are not only less able to avoid hunters but are also less able to avoid their other predators.

(B) Human beings generally have a substantial degree of biological immunity to the diseases carried by other species.

(C) Very few species of North American animals not hunted by the new arrivals from Asia were extinct 2,000 years after the first migrations.

(D) Individual humans and animals can carry a disease-causing microorganism without themselves suffering from the disease.

(E) Some species of North American animals became extinct more than 2,000 years after the arrival in North America of the first prehistoric human migrants from Asia.

Source: LSAT