You are presented with the quiz "What can have a long term effect on crops and weather conditions around the world?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "gases released during the use of fossil fuels causes global warming" and "global warming has great effect on crops and weather conditions around the world". 

So, what's the best answer to the question?


 

      Use of fossil fuels     