第29题: [单项选择]市话全塑电缆按用途可分为()两种电缆。 A. 全色谱和普通色谱 B. 铜导线和铝导线 C. 填充型和非填充型 D. 传输数字信号和传输模拟信号 参考答案:D
第30题: [单项选择]Hydrocarbons, ______ by engine exhausts, react with nitrogen oxides in the presence of sunlight to form complex toxic gases. A. are given off B. give off C. they are given off D. given off 参考答案:D