Explain why people are building green roofs to live healthier lives.

Green roofs help reduce the Urban Heat Island Effect, a condition in which urban environment absorb and trap heat. A green roof's plants remove air particulates produce oxygen and provide shade. Another important benefit of green roofs is their ability to reduce and slow stormwater runoff in urban environment.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.