【单选题】下面哪一个是模拟数据用数字信号传输的模型?
【判断题】《产品质量法》规定,生产者不得生产国家明令淘汰的产品;不得伪造或者冒用认证标志等质量标志。
【单选题】三极管基本放大电路输出波形如下图所示,请问(a)图发生( )失真,(b)图发生( )失真.
【单选题】I didn't hear the phone. I _____ asleep. [ ]
【单选题】I didn’t hear the phone. I ___asleep. A. must be B. must have been C. should be D. should have been
【单选题】______ it______ for your help,I couldn't have made any progress.
【单选题】一位美国学者曾说在自家的院子里有印钞机是一件愉快的事情,而黄金兑换标准给了我们这个特权。”赋予“我们这个特权”的是( )
【单选题】— I feel _____a pity that I haven't been to the get together. — You really should have. [ ]