我发誓我离开时锁了前门。

I could have ___sworn that I locked the front door when I left.

我敢肯定我今天早上在厨房桌子上看到你的钥匙了。

I could have ___sworn I saw your keys on the kitchen table this morning.

他发誓他告诉过我关于会议的事，但我一点印象都没有。

He ___swore he had told me about the meeting, but I had no memory of it.