let down

... let down：放低；放下；拿下；使失望；对……失约 let in：让进来；放进；漏水 let off：让（某人）上岸或下车；放（炮、烟火等），放过；原谅 ...

 keep down

... keep company with=与...来往,与...结成同伴 keep down=节制,压制,弹压;放低(声音) keep from=使...不(做) ...

 lower

... low 低的 lower 放低 mown mow(刈)的过去分词 ...