in a moment 适用于将来时，表立刻，马上，一会儿。例句i'll be back in a moment.for a moment 是指“片刻”、“一会儿”，表示持续的时间。例如：For a moment she just stood there, unable to believe what had just happened. at the moment 的意思是“现在”“此刻”，常与一般现在时或现在完成时连用。例如： I have got enough to do at the moment. 但是，at the moment 有时也作“当时”讲，用于过去时态。例如： I didn't buy that boo...
