I think I will try my best to ｝solve the pollution problems.

I think I will try my best to ｝solve the pollution problems.
I think I will try my best to ｝solve the pollution problems.

I think I will try my best to ｝solve the pollution problems.
其实,I think I will try my best to solve the pollution problems 是一个完整的句子.按照语法来说,不用在中间加什么.

这个空不需要填词
因为从句中的 try one's best to do sth 是固定搭配 “尽某人最大努力去做某事”