on a morning 还是in a morning

on a morning 还是in a morning in a cold morning还是on a cold morning? 是on a cold morning 还是in a cold morning? on a sunny morning 还是in a sunny morning 是on a fine morning还是in a fine morning? in the morning,on a winter morning 用in a sunny morning 还是on a sunny morning?为什么?那on Sunday morn 请问是In a cold winter morning 还是 on a cold winter morning? 是on a cold winter morning还是in? a cool morning前面用in 还是on ( ) a cold morning of november,on还是in? ---------a Sunday morning 是用in还是on?