1、表示“在何时”常用介词at, on, in等A. at一般用来表示在某一具体的时间点at ten o\'clockat the weekendat that timeat the age ofB.on用来表示某天或某天上下午on January 1ston the following dayon Monday afternoonon a cold winter eveningC.in 用来表示一段时间,还可用在月、季节、年等时间短语前。in the morningin springin Augustin a minute