I was born （ ）a sunny day. A.on B.at C.in D.for 应该选用哪一个介词

英语里表示“在”的时间介词：

1)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 one’s life , in one’s thirties等。

2)on表示具体某一天及其早、中、晚。

如, on a sunny day, on May 1st, on Monday, on New Year’s Day, on a cold night in January, on a fine morning, on Sunday afternoon等。

3)at表示某一时刻或较短暂的时间，或泛指圣诞节，复活节等。

如at 3:20, at this time of year, at the beginning of, at the end of …, at the age of …, at Christmas， at night, at noon, at this moment等。

题目中a sunny day为具体的某一天，所以选A. on

希望能帮助你！