A:11
B:16
C:40
D:50
As long as I can remember, ___________I called, his wife would answer the phone.
在平面内,设A,B为两个不同的定点,动点P满足:PA→·PB→=K2(k为实常数),则动点P的轨迹为( )
下列各项中划线的词语使用不恰当的一项是( )