I hope / we / able / solve the problems / over population and pollution

A. I hope whether we are able to solve the problems, those are over population and pollution. 

B. I hope if we will be able to solve the problems, which are over population and pollution.

C. I hope that we will be able to solve the problems of over population and pollution.

D. I hope when we will be able to solve the problem for over population and pollution.