lit. three monks have no water to drink (idiom) / fig. everybody's business is nobody's business / (If there is one monk, he will fetch water for himself. If there are two, they will fetch water together. But if there are three or more, none will take it upon himself to fetch water.)
关你屁事
guān nǐ pì shì
(coll.) None of your goddamn business! / Mind your own business!
雨女无瓜
yǔ nu:3 wú guā
(neologism) (slang) it's none of your business (imitation of an accented pronunciation of 與你無關|与你无关[yu3 ni3 wu2 guan1])
莫属
mò shǔ
(the 3rd part of a 3-part construction: 非[fei1] + (noun) + 莫屬|莫属, meaning "to be none other than (noun) / would have to be (noun)") (this construction comes after a description of a person or thing that has a certain attribute)