改错不懂!The problems that are created by environmental contamination are very hard to resolve.

题目

改错不懂!The problems that are created by environmental contamination are very hard to resolve.
我总觉得这句话不通,为什么第一个are可以要呢?可不可以讲that后面的那个are去掉呀?
书上原题是：The problems that are created by environmental contamination is very hard to resolve.
然后改为这：The problems that are created by environmental contamination are very hard to resolve.
可是我觉得改过的也不懂，总觉得第一个are怪怪的，还有that是个什么从句呢？如果是从句，那第一个are在句子中是什么成分呀？

答案

that不可以去掉,但是可以同时去掉that are 这样created就是相当于个形容词,不做谓语成分了.前面的that是定语从句的标志.