It's cold this morning. 今天早上好冷。

(1) 改为过去式
—> It was (It's) cold this morning.

(2) 改为附加疑问句/反义疑问句
—> It's cold this morning, isn't it?
附加疑问句/反义疑问句的句型是:
如果是肯定句: 主句肯定陈述句+否定附加疑问句
如果是否定句: 主句否定陈述句+肯定附加疑问句
比如，..., aren't you? / ..., didn't they? / ..., is he?
附加疑问句常用于征求对方的同意或者确认什么事情。

(3) this moring 换成 last night，并且改为疑问句
—> Was it could last night?
先把 this moring 换成 last night 就是 It's cold last night. 再换成疑问句就是 Was it could last night?