But others don't agree.这句话对么,总觉得应该为：But others don't agree it
答：agree作为及物动词,只跟不定式作宾语：agree to do sth.
作为不及物动词,必须跟上一个介词后才可能跟名词或代词：agree on/to/with +名词/代词.
所以：But I don't agree.是正确的.是I don't agree with you 之省略.即我不同意你的观点.
2.They don't think everyone has to communicate with foreigners in the future.和They think not everyone has to communicate with foreigners in the future.哪个句子正确呢?为什么?
答：两句话都是正确的.
前句意为：他们不认为将来人人都得和外国人交流.
后句意为：他们认为,将来不是所有人都得与外国人交流.
析：一开始我以为后一句在现在英语中是错词的,因为不说They think not (that)-宾语从句,因为现代英语,think这个谓语的否定不是在后加not而是don't think,
后来一看,这一句可以是：They think (that) not everyone has to communicate with foreigners in the future.
而：Not everyone has to communicate with foreigners in the future.
=Everyone doesn't have to communicate with foreigners in the future.
作为部分否定句子,是正确的.
另外,think作为谓语,其后面的宾语从句的否定不是一定要移到前面来的,看需要.
某人可以有一个肯定的想法：sb.thought that sth.would happen.
也可以有一个否定的想法：sb.thought sth.would not happen.
当然也可以没有一个肯定的想法.sb.didn't think sth.would happen.
至所以说：I don't think you are right.只不过是“我”想表达得委婉一些罢了.在需要的时候,我就说：I think that you are not rigth.=I think that you are wrong!