Y3150E型滚齿机不能加工（）。
A.直齿圆柱齿轮
B.斜齿圆柱齿轮
C.内齿轮
D.蜗轮
参考答案：C
脑性瘫痪的主要病因
A．早产
B．脑外伤
C．胎盘早剥
D．弓形虫感染
E．脑炎与脑膜炎
一He's never seen to eat so much food, ______?
一No, he always eats a little. [ ]
A. is he
B. isn't he
C. has he
D. hasn't he
