【单选题】We have been studying English .
【单选题】I have waited for her since _____.
【单选题】Miss Gao has taught us English two years. I have been here two years ago. [ ]
【单选题】分析阻容耦合低频小信号放大电路时,通常采用交流量和直流量分开的方法,这是由于( )
【单选题】He has been running______.
【单选题】I haven’t seen you ____________.
【简答题】在低频小信号放大电路的分析中,直流通路中电容视为(),交流通路中大电容可视为(),已知负载开路时输出电压为2V,接入2千欧负载电阻后输出电压变为1V,则放大器的输出电阻约为()
【单选题】The twins has studied in this school ________ .