What is the biggest green building district in the world?

i think the  King Abdullah Financial Center, Riyadh Saudi Arabia is the true answer

in my opinion i think masder city is one 

In my opinion its B- King Abdullah Financial Center, Riyadh Saudi Arabia. Really its a big one.

Out of my specialty but I think Option C

Thanks for your invitation

C, because there is many big building according to a towns such as in USA & UK, or in europ.

Thank you. Option B is appropriate answer.

Thanks for the invitation. The question is out of my specialty.

B- King Abdullah Financial Center, Riyadh Saudi Arabia.

Thanks for the invite. My answer is B