虽然不知道为什么，但我必须说抱歉！

Why although doesn't know, but I must say sorry!

youdao

他自己觉得很清醒，甚至充满活力，虽然他不知道为什么。

He himself was feeling quite wakeful and even lively, though he didn't know why.

youdao

虽然她不知道为什么，但她已经觉得不那么“倔”了。

Already she felt less "contrary", though she did not know why.

youdao

But I was convinced I'd hear the click-click-click-click-click which is what tells you you're in trouble.

我总会觉得很紧张，我不知道这是为什么,虽然我从来没有接触过放射元素。

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