swear to   (TTS發音)

assert with great conviction 斷言；發誓肯定

    I can't swear to it，but I don't think he would lie to me. 我不敢斷言，但我認為他不會對我撒謊的。

    I was sure I locked the door when I left the room，but I can't really swear to it. 我離開房間時肯定是鎖了門的，但我不能把話說死。