the failure is because of her vain 这句话错了么?如果错了,错在哪里?请解释一下~

vain 徒劳的；虚荣的；空虚的
这是形容词
而 because of 后面只能跟名词 ,改为her vanity原句是vanity..我少打了那改成vanity就对么？是的。改为vanity至少语法上正确了。具体语义还要看你的上下文。或者 不用because of 用 due to 也可以。这个句子是我改的= =给你看看原题!!The shift from traditional to cosmetic dentistry （ ） more vain.A. is because adults are getting fewer cavities and becoming B. is because of adults getting fewer cavities and their becomingD. is occuring because adults are getting fewer cavities and becoming答案是D请分析一下AB为什么不对!!尤其是BB 中their不对，不能用所有格吧To be honest, A 真没看出有什么不对。毕竟because 除用于引导原因状语从句外，还可引导表语从句。如：It is because he is too foolish. 那是因为他太蠢了。只是感觉有些Chinglish。一般说 It's because ... 用得多些。很少看到前面主语有这么长的，一般都用代词代替了。或许改为下面这样说法比较正统些：The shift from traditional to cosmetic dentistry is occuring. It's because adults are getting fewer cavities and becoming more vain. 个人感觉，A和B被排除的最主要理由可能是：主句没交代清楚时态，到底是正在发生的还是已经完成的。如果已经完成，那么从句的时态就有问题了，整个句子的语义也有问题。