他的借口听起来很不靠谱，没人相信他的话。

His excuse sounded so ___unconvincing that nobody believed him.

他的借口听起来很假，没人相信。

His excuse sounded ___unconvincing, and nobody believed it.

他的借口听起来非常不可信，没人愿意相信他。

His excuse sounded very ___unconvincing, and no one was willing to believe him.