Maybe I could turn toward him, hold up the cover of the book and say in my crying voice, "I'm sorry, sir."

也许我可以转向他，举起书的封面，用哭泣的声音说：“对不起，先生。”

youdao

I'm sorry to forget to bring your book back. I left it in my bedroom.

对不起，我忘了把你的书带回来。我把它忘在我的卧室里了。

youdao

I'm sorry that we don't have this book in our collection. But could I recommend another book for you, or can we borrow one for you through ILL?.

对不起，我馆没有这本书。我能向您推荐另一本书吗，或试一试馆际互借。

youdao