单项选择题
In a certain digital waveform, the period is twice the pulse width .The duty cycle is 在某一数字波形中，周期是脉冲宽度的二倍。则其占空比为：
单项选择题 基因扩增是原癌基因激活的机制之一。 A、正确 B、错误
单项选择题 ________specifically tells the story of Meng Jiangnv. A、Yuju Opera B、Mengxi Opera
单项选择题 ___ take precedence over all social relationships; therefore nepotism is somewhat customary in many business environments and viewed in a positive way.（ ）
