在旋毛虫病流行中起重要作用的传染源是
A．蛇
B．狼
C．旋毛虫病带虫者
D．旋毛虫病病人
E．猪
参考答案：E
A great many teenagers became ________ playing computer games, wasting their precious time. [ ]
A. accustomed to
B. addicted to
C. used to
D. due to
下列钢号中，（）是锅炉用钢。
A.16MnR
B.20
C.20g
D.A3F
