In a position like this, one can ________ stand up _______ lie down . So it is very uncomfortable.
A:both… and…
B: either… or…
C:neither… nor….
D:not only… but also…
如图为两种生物种群的生长曲线,以下说法错误的是( )
(1)已知⊙O的直径为10cm,点A为⊙O外一定点,OA=12cm,点P为⊙O上一动点,求PA的最大值和最小值.
(2)如图:=,D、E分别是半径OA和OB的中点.求证:CD=CE.