3 sentences

1. 他的话听起来非常可信。

   tā de huà tīng qi​lai fēi​cháng kě​xìn.

   What he says sounds very credible.

   Source: Dong Chinese Dictionary

2. 她的证词不可信。

   tā de zhèng​cí bù kě​xìn.

   Her testimony cannot be trusted.

   Source: OpenSubtitles

3. 这仅仅是一个谣传，并不可信。

   zhè jǐn​jǐn shì yī gè yáo​chuán, bìng bù kě​xìn.

   This is merely a rumor and is not credible.

   Source: Dong Chinese Dictionary