【单选题】构件在发生断裂破坏前,有明显先兆的情况是( )的典型特征。
【单选题】只放大电流,不放大电压的放大电路是( )。
【简答题】The sudden ( ) of the fairy made the children in the cinema break into cheers. (appear)
【简答题】The sudden (appear) ________ of a policeman caused the thief to run away.
【简答题】请画出图中指定物体的受力图。未画出重力的物体其自重不计,所有接触处均为光滑接触。 2-2,