他说话总是那么斩钉截铁，让人很难反驳。

Tā shuōhuà zǒngshì nàme zhǎndīngjiétiě, ràng rén hěn nán fǎnbó.

He always speaks so firmly that it’s hard for others to refute him.

面对质疑，她斩钉截铁地表示自己没有说谎。

Miànduì zhìyí, tā zhǎndīngjiétiě de biǎoshì zìjǐ méiyǒu shuōhuǎng.

Facing doubts, she stated firmly that she had not lied.