He is going to            a pilot when he            up. [ ]

A. do, grow

B. do, grows

C. be, grow

D. be, grows

（）都是柱体。

A.Z=（X2+Y2）/-30

B.X2/100+Y2/50+Z2/40=1

C.Z=X2/30

D.Z=X2/100-Y2/70

E.X2+Z2=100