A great number of students said they were forced to practise the piano.
A:to question
B:to be questioned
C:questioned
D:questioning
如图,半圆的直径AB=6,O为圆心,C为半圆上不同于A、B的任意一点,若P为半径OC上的动点,则 PA→+PB→·PC→的最小值为( )
肾脏的结构和功能的基本单位是( )
已知x2﹣2x=5,则x的值为____.