Alternating current as a source of power has certain advantages over direct current. 前后两个下划线介词短语分别充当_______。
                    举一反三
- 中国大学MOOC: Alternating current(交流电) as a source of power has certain advantages over direct current(直流电). 前后两个下划线介词短语分别充当_______。
 - A circuit may be defined as a path for current flow. 前后两个下划线介词短语分别充当_______。
 - The function of direct current regulated power supply is to input an alternating current power of 220volts, so that it can output __________.( ) A: alternating current 200 volts voltage B: direct current 24 volts voltage C: direct current 200 volts voltage D: alternating current 24 volts voltage
 - The resistance of the load is too high for the amplifier. 前后两个下划线介词短语分别充当_______。
 - 中国大学MOOC: The resistance of the load (负载)is too high for the amplifier(放大器). 前后两个下划线介词短语分别充当_______。
 
