ought to help each other in our work,

ought to help each other in our work,
We ought to help each other in our work,
A.oughtn't we
B.should we
C.shouldn't we
D.ought to we
想问问能不能选C,我前几天在一个百度知道问题里找到有ought to的反义疑问句可以用shouldn't和oughtn't,很多次发现有的人采纳了错误的答案,真伤脑筋呢,百度知道什么时候也弄个最佳答案正确性大扫除项目也好了