A:完善自己
B:悦纳自己
C:认识自己
D:发展自己
Unless ______ to speak, you should remain silent at the conference.
如果实数x,y满足x≥0y≥02x+y≤2,对任意的正数a,b,不等式ax+by≤1恒成立,则a+b的取值范围是( )
—There are eight.