what should i get my sister?-why don't you get her a camera?-why not to get her a camera?-why don't get her a camera?这三个句子哪个是对的?哪个是错的?为什么?

what should i get my sister?-why don't you get her a camera?-why not to get her a camera?-why don't get her a camera?这三个句子哪个是对的?哪个是错的?为什么?
what should i get my sister?
-why don't you get her a camera?
-why not to get her a camera?
-why don't get her a camera?
这三个句子哪个是对的?哪个是错的?为什么?

what should i get my sister?-why don't you get her a camera?-why not to get her a camera?-why don't get her a camera?这三个句子哪个是对的?哪个是错的?为什么?
正确的句子应该是第一个
-why don't you get her a camera?
这句话是正确的.
why not do sth
为什么不做……这是一个提建议的方式,是固定搭配.
或者是why don't sb do sth
为什么（某人）不做……和上面的意思用法是相同的.
所以只有两种方式,要么是why not get her a camera?
要么是why don't you get her a camera?
其他的都是错误的,所以只有第一句是正确的.

果断选第一个嘛！！！！

why don't.... is correct

正确的句子是第一个，第二个是要去掉中间的那个to，第三句加上you就对了，why not后面的动词不定式是不带to的。希望我能帮助你解疑释惑。