Https://healthresearchfunding.org/marcellus-shale-pros-cons/   this site will give you the pros and cons
        
             
        
        
        
This is true because 6 and 15’s sum is 21.
        
             
        
        
        
The best answer is reduction in acid rain.
Acid rain is rainfall which has been rendered acidic by pollutants  in the atmosphere.  This kind of rain is typically harmful to  forests and lakes.
The main cause of acid rain is human activities. The burning of fossil fuels such coal in electrical generating plants and crude oil products such as gasoline and diesel in car engine  releases  sulphur dioxide and nitrogen oxide into the atmosphere. 
These compounds mix with water very high up in the atmosphere and form acid pollutants which  fall on the ground as acid rain.
 Use of clean energy will eliminate burning of fossil fuels and thus no acid rain will be produced.
 
        
                    
             
        
        
        
The physical processes on Earth create constant change. These processes—including movement in the tectonic plates in the crust, wind and water erosion, and deposition—shape features on Earth's surface.Lithospheric Processes cause magmatism, mantle dynamics, and faulting, which in turn shape the Earth's ever-changing surface.
The four common Planet Surface Processes are: Cratering, Volcanoes, Erosion, and Weathering (chemical and physical).The Earth's surface is constantly changing through forces in nature. The daily processes of precipitation, wind and land movement result in changes to landforms over a long period of time. Driving forces include erosion, volcanoes and earthquakes.
Lithospheric Processes. Lithospheric Processes cause magmatism, mantle dynamics, and faulting, which in turn shape the Earth's ever-changing surface. ... We also study the high temperature systems in the Earth's interior that produce magmas, drive metamorphism, and create mantle heterogeneity.
I hope it will help you