英语知识 in on at to for of with等介词的用法,最好有例句,答:1)in , on,at 在……时 in表示较长时间,如世纪、朝代、时代、年、季节、月及一般(非特指)的早、中、晚等. 如in the 20th century, in the 1950s, in 1989, in summer, in January, in the morning, in the night, in one’s life , in one’s thirties等. on表示具体某一天及其早、中、晚....