克里普克提出了刚性指称词的概念。

Kripke introduced the notion of the ___rigid designator.

这张金属桌子非常坚硬，无法弯曲。

The metal table is so ___rigid that it cannot bend.

他的教学方式过于死板，从不接受学生的建议。

His ___rigid teaching style never accepts students' suggestions.

听到突然的巨响，他僵在原地一动不动。

He stood ___rigid in place at the sudden loud noise.