【单选题】Tim is working for a big firm. He is working for a big ___________.
【单选题】The crankshaft receives and transmits the full working power of the engine and is subjected to fluctuating _____.
【单选题】哪一个电压等级的电气设备属于低压电气设备
【单选题】下面哪个是选择拍摄商品图片的数码相机时要考虑的要素 ?( )
【单选题】The local people were amazed to find that these volunteers were working to their full ______.