The postman delivered a letter this morning.(Who)怎么变成疑问句

Who delivered a letter this morning?
这里向人提问，那么疑问句中就要把人换掉。
11点15分是a quarter past eleven.
或是eleven fifteen.

Who delivered a letter this morning?

直接写11:15就可以了
如果非要用英语写，eleven fifteen或者a quarter past eleven都可以。

Who delivered a letter this morning?

fifteen past eleven 或 eleven fifteen

Who delivered a letter this morning.
A quarter past 11

Who delivered a letter this morning?

11:15 = Fifteen past eleven / eleven fifteen / a quarter past eleven

11.15 a quarter past 11
疑问句 Who delivered a letter this morning?