Ethologist Irenaus Eibl-Eibesfeldt (1963)raised Rats in Isolation

Ethologist Irenaus Eibl-Eibesfeldt (1963) raised rats in isolation.When other rats were finally introduced into their cages,rats raised alone _______,suggesting that _______.

A) fled from the new rats; aggression must be learned.
B) used the same aggressive behaviours as other rats; aggression need not be learned.
C) did not aggress against them; instrumental aggression does not exist in nonhumans.
D) could not defend themselves; aggression is learned.
E) become more aggressive than other rates; isolation leads to aggression.