防止放射性物质经呼吸道进入体内的基本措施不包括（）
A.净化空气
B.减少放射性物质的使用
C.稀释
D.密闭包容
E.个人防护
参考答案：B
________ at the theatre, he found the ticket his friend gave him was left at home. [ ]
A. To arrive
B. On arriving
C. While arrived
D. On arrived
绝缘体是这样一种物质 [ ]
A．没有电荷
B．没有正电荷
C．没有电子
D．几乎没有自由电荷
