CRH1A型动车组拖车每根轴装有（）副制动盘。
A.1
B.2
C.3
D.4
参考答案：C
丝虫致病的主要阶段是（）
A.微丝蚴
B.腊肠蚴
C.丝状蚴
D.杆状蚴
E.成虫
The period during when people learned to smelt iron is called the Iron Age.
