We want five good singers _______ our rock band. [ ]
A. for
B. to
C. on
D. at
答案:A
已知函数f(x)对任意x,y∈R,满足f(x)+f(y)=f(x+y)+2,当x>0时,f(x)>2.
(1)求证:f(x)在R上是增函数;
(2)当f(3)=5时,解不等式:f(a2-2a-2)<3.
生态系统的生物组分有哪三大功能类群试论述各类群的生态功能。