And I swear that it's true.

我发誓这一切都是真的。

youdao

When grandmother lives, i felt that she's very pitiful, and i swear that i would treat her well when i grew up.

祖母还活着的时候，我觉得她很可怜，我发誓等我长大后我一定要对她好。

youdao

That means you can use "I" and "you", you can use slang, you can even swear if it fits your site's purpose.

就是说，你可以作用“你”和“我”，可以用俚语。如果与网站本身的目标没有冲突的话，你甚至可以用发誓的口吻。

youdao

Unidentified Man: I, Pervez Musharraf, do solemnly swear that I am a Muslim and believe in the unity and oneness of Almighty Allah.

NPR: Musharraf Sworn In, Promises to Lift Emergency