埋藏在海洋深处的可燃“冰”,其主要成份是( )
A.SiH4
B.H2
C.CO
D.CH4
答案:D
P、Q、R三点在同一条直线上,一物体从P点静止开始做匀加速直线运动,经过Q点的速度为v,到R点的速度为3v,则PQ∶QR等于[ ]
A.l∶8
B.l∶6
C.l∶5
D.1∶3
He hopes his son _________ a doctor in the future.
A.to be
B.be
C.will be
D.to become