“—下” is used after a verb to indicate a short action, similar to the reduplicative form of a verb. The object of the verb can be omitted. For example: wǒ kàn yí xià shū 。 我看一下书。Let me read the book. nǐ xiū xi yí xià bɑ 。 你休息一下吧。You can take a break. nǐ wèn yí xià lǎo shī 。 你问一下老师。You ask the teacher. wǒ tīnɡ yí xià zhè shǒu ɡē 。 我听一下这首歌。Let me listen to this song.