Which detail from the passage BEST supports the idea that green roofs can help cities decrease their power consumption?

O A Che planario all yer he ountry are intiating
Over 400 green roof projects are being
• B. developed in Chicago.
c Route garment improve air qualiy and
Energy costs at City Hall in Chicago decreased
O D after a green root was installed there.

Energy costs at City Hall in Chicago decreased after a green roof was installed there.