-Do you know what speed _______ for a rocket to escape from the pull or gravity of the earth to

send a satellite into outer space?   

-No idea at all. I have never got the ______ of it.     [ ]

A. it needs; idea  

B. is taken; hang  

C. is needed; hang  

D. it takes; thought

韩-薛-柯病的最好发于()

A．颅骨

B．眼眶

C．骨盆

D．股骨

E．脊椎