已知:⊙O的直径等于4,点P到圆心O的长度OP=4,则点P与⊙O的位置关系为( )
A:P在⊙O上
B:P在⊙O内
C:P在⊙O外
D:不确定
设全集UR实数集RM=(-∞,-2)∪(2,+∞)N={x|x2-4x+3>0}则图中阴影部分所表示的集合是 ( )
-- Many students don't know what to stress and become worried.
-- I think they'd better ask their teachers for help.
下列关于植物激素的叙述,错误的是
—Yes,I have. I've _______improved it a lot.