在y=()x, ,y=x2, 四个函数中,当0<x1<x2<1时,使f()>恒成立的函数个数是( )A. 0B. 1C. 2D. 3 答案:解析:如图,设A(x1,y1),B(x2,y2),则f()表示C点函数值,表示D点函数值.本题主要考查函数图象是上凸还是下凹.答案:C() 1. They got married 1960. That means they have been married 1960. A. at; since B. on;in C. in;since D. for;since