【简答题】电子学研究的对象是载有信号的电信号,按其特点可以分为模拟信号和数字信号。模拟信号的特点是 ,数字信号的特点是 。
【简答题】数字信号的特点是 ,模拟信号的特点是 。
【单选题】They didn't watch the TV play that day, and______.
【单选题】We used to have a discussion, ___?
【简答题】We didn’t go fishing because it rained heavily.(改为同义句) We didn’t go fishing________ ________ the heavy rain.