第2题: [单项选择]The twentieth century has been a period of enormous growth in mathematical research and in the number of mathematicians and fields __________them. A. they require B. requiring C. require D. as required 参考答案:B
第3题:[多选题]下列说法中不正确的是( ) A. 状态寄存器S一定要按编号从小到大使用 B. 所有的定时器都是100毫秒型的 C. PLC的工作方式是串行扫描 D. M8002是特殊辅助继电器 参考答案:AB