I really must say good-bye.

真的要说再见了。

youdao

He really must be careful about thinking aloud. Who knew what he might say?

他真地得对自言自语小心点。谁知道他可能会说什么？

《柯林斯英汉双解大词典》

And it's really very unexpected, I must say.

我必须说，这真的非常出人意料。

youdao

Say, you look fine. You must really be doing okay down here.

你气色很好啊,一定在下面过得不错

耶鲁公开课 - 古希腊历史简介课程节选

but you have a prior engagement and you really must be going, you can say,

但是你已有约在先，你真的必须走了，你可以说，

I wish 课堂 - SpeakingMax英语口语达人

There was nothing analytic about that and I was really, I must say, surprised at how little they had thought about what do we do and how do we do it.

FORBES: The Early Years

Ms. THURSTON: It really can, and I must say that it is the first time something like this has ever happened, that the parish president has ceded control.

NPR: Hurricanes Wreak Havoc In Haiti And Cuba

The most persuasive argument someone could make is an argument against their own interest because you say wow, that person must really mean what they're saying.

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