Answer:
burning of coal 
Explanation:
Coal contain carbon which combines with oxygen.
 
        
             
        
        
        
Yes biotic means living or once living. it was living at one point so yes its biotic
        
                    
             
        
        
        
This is true. Hope this helps.
        
                    
             
        
        
        
Answer:
Outer Core of Earth
Explanation:
The outer layer of core of earth consists of iron as a major constituent. Due to internal high temperature and low pressure (as compared to the inner core) , the iron in this layer exists as liquid iron. Since the earth is rotating continuously on its axis, the liquid iron is also rotating thereby producing magnetic field. Due to magnetic field , this sphere of earth is known as magnetosphere.