研究动物行为的根本目的是[ ]
A.保护有益动物,消灭有害动物
B.掌握动物行为的变化规律
C.保护动物的多样性,利用有益动物和防控有害动物
D.认识和了解动物
答案:C
19. --- Could you tell me how the sea sand comes about ?
--- Sea waves dash against the rock. In this way , the sea sand ___ .
A.comes into use
B.comes into office
C.comes into effect
D.comes into being
正态曲线与小于(μ-1.96σ)的横轴所夹面积等于
A.0.05%
B.0.1%
C.0.5%
D.2.5%
E.5.0%