单选题
[阅读选择]War may be a natural expression of biological instinct and drives toward aggression in the human species. Natural impulses of anger， hostility， and territoriality （守卫地盘的天性） are expressed through acts of violence. These are all qualities that humans share with animals. Aggression is a kind of innate （天生的） survival mechanism， an instinct for self-preservation， that allows animals to defend themselves from threats to their existence. But， on the other hand， human violence shows evidence of being a learned behavior. In the case of human aggression， violence can not be simply reduced to an instinct. The many expressions of human violence are always conditioned by social conventions that give shape to aggressive behavior. In human societies violence has a social function： It is a strategy for creating or destroying forms of social order. Religious traditions have taken a leading role in directing the powers of violence. We will look at the ritual and ethical （道德上的） patterns within which human violence has been directed.
Human violence shows evidence of being a learned behavior in that ______.
A.it threatens the existing social systems
B.it is influenced by society
C.it has roots in religious conflicts
D.it is directed against institutions of law
正确答案：B
答案解析：本段指出了人类暴力的两个特性，其中第二个特性是“a learned behavior”。可以知道本题的答案应该就在本段的后面部分。接下来的第二句话即说人类暴力的诸多表现形式都受社会习惯的制约：The many expressions of human violence are always conditioned by social conventions that give shape to aggressive behavior，将其定型为侵略性行为。