当他笨拙地摔倒在泥坑里时，周围的人都忍不住窃笑起来。

Everyone couldn't help but ___snicker when he clumsily fell into the mud puddle.

听到这个荒谬的借口，她忍不住发出一声窃笑。

She couldn't help but let out a ___snicker at the ridiculous excuse.