他因为踩到乐高积木而脱口骂出几句脏话。

He let out a few ___expletives after stepping on a Lego brick.

在句子'It is important to study'中，'it'是一个虚词，没有实际意义。

In the sentence 'It is important to study,' '___it' functions as an ___expletive without real meaning.