Why not ________ an English Club to practice ________ English?
A:to join; speaking
B:join; speaking
C:join; to speak
D:to join; to speak
下列有关基因对性状的控制的说法不正确的是( )
x
2
3
4
5
6
y
2.2
3.8
5.5
6.5
7.0
如图,电灯P在横杆AB的正上方,AB在灯光下的影子为CD,AB∥CD,AB=2m,CD=5m,点P到CD的距离是3m,则点P到AB的距离是( )