为什么是on a cold night,in a sunny morning

为什么是on a cold night,in a sunny morning 英语介词问题on a cold night为什么是on a cold night 不是in a cold night 或者是at?是因为有cold这个形容词修饰night吗? 时间前面什么时候+on/in具体时间+on,我知道,那什么时候+in?为什么是On a cold night?a cold night是一个不确定的时间吧,为什么用on呢?那如果没有定语cold，就是night用in还是On？ the murder____(happen) on a cold night on a cold night为什么要用介词on On a snowy night为什么是on不是at the night或者in the evening吗 night什么时候用介词on什么时候用at比如at night ,on school night,on a cold night ( ) a cold winter night.是用in还是on? It was a cold night when he was on duty There was a heavy snow last night.This morning is _______ outside.A.too rather cold B.rather too cold C.such cold D.fairly cold答案为什么是B,而不是 D 为什么有时候用at night ,有时候用on a cold night .It was so cold that the travelers had the fire _____ all the night..It was so cold that the travelers had the fire __A____ all the night.A.burning 为什么是doing? i am having a surprise party for lana on Friday night中为什么是am having? The poor man died ( )a cold winter night.A inB at C byD on （—）a cold winter night 中间填什么介词.in还是on. The story happened_____a cold night A.in B.of C.on D.at 为什么是on a clear night,在晚上不是用at night吗原题是It's fun to see a large number of stars shining in the sky ________ a clear night.　　A.at B.in C.on D.of so cold a day中cold a day为什么是adj啊?而a cold day是名词啊?