on cold days 冷天气的作用下的意思
Why can you see your breath outside on a cold day?
in the days 在那些日子里
She was happy in those days什么时候用on，什么时候用in？on cold days 冷天气的作用下的意思 卫生莫冷天气时再室外可以看到自己哈出的气 in the days在那些日子里 She was happy in those days她在那些日子里很快乐意思不一样喔