常用in、on、at作介词开头的词组答:时候), on the spur of the moment(立刻) on this day, on this occasion, on time,at at a time(在某时), at a wedding(婚礼), at all times(一直), at any moment, at any time, at Christmas, at dark (天黑时), at dawn(在黎明), at daybreak, at dinner-time, at dusk(...