____a tiger ____ fur? [ ]
A. Does; has
B. Do; have
C. Does; have
答案:C
设函数y=f(x)(x∈R)对任意实数均满足f(x+y)=f(x)+f(y),求证f(x)是奇函数.
药物敏感试验方法主要有()、()、(),采用的培养基为()肉汤或琼脂。