The movie “The Time Machine” is a science fiction story.
A:base on
B:basing on
C:based in
D:based on
已知a1,x,y,a2成等差数列, b1,x,y,b2成等比数列.则(a1+a2)2b1b2-2的取值范围是 ( )
植物的许多器官都能繁殖后代,用下列器官繁殖属于有性生殖的是( )