各类文档，记录单据保管期为二年的：（）
A.无线电信号书
B.电台工作日志
C.气象报告和航行报警
D.设备维修记录
参考答案：B
A middleman's work may become difficult because ______.
A．manufacturers run their production on a much higher level
B．market demand may not be the same as industrial production
C．retailers are not necessary in running their retailing business
D．retailers demand lower levels than those demanded by manufacturers
工业区用地应选择城市中卫生条件最好的地段。()
