两个物体的主视图都是圆，则这两个物体可能是[ ]
A．圆柱体、圆锥体
B．圆柱体、正方体
C．圆柱体、球
D．圆锥体、球
答案：C
With more and more people__________ the importance of English, English training has become a profit-making industry.
A．have realized
B．realizing
C．to realize
D．having realized
点火通氨前要旋转点火臂，确认（）正常。
A.氢气压力
B.气密性
C.电机运转
D.铂网
