Who cares是正确的写法。
1、原因
who疑问代词作主语，属于单数第三人称，要用单三谓语形式。表示某事对你来说不重要。所以care要加s。
2、意思
Who cares：管它呢；谁在意；管他呢；谁说我不在乎；不在乎。
3、例句
Who cares about some stupid vacation?
谁在乎什么愚蠢的度假？
The woman tells anyone who cares to listen that she's going through hell
只要一有人听她诉说，那个女人就会告诉人家她正在受苦受难。
同义句型解析：
①、not mind
意思：不在乎；不介意
The fashion world does not mind what the real world thinks.
时尚界并不在意现实世界的想法。
Love is born of heart, not mind.
爱情生于情感而不是出于理智。
②、not care
意思：不在乎；不介意
She had met both sons and did not care for either.
两个儿子她都见了，一个都不喜欢。
He did not care a snap to talk loudly in class.
他毫不在乎地在课堂上大声讲话。
