निम्नलिखित में से कौन-सा कारक पर्यावरण अवनयन (पर्यावरण क्षरण) में योगदान नहीं देता है?

The atmospheric phenomenon where falling raindrops absorb and remove pollutants below the cloud level is called:

Which Indian state was the first to make rooftop rainwater harvesting compulsory for all houses across the state?