Answer:
I think it might be A. I'm not sure.
 
        
             
        
        
        
The answer for this would just be your opinion. 
how confident are you in answering the question, if you are not confident than say you aren’t and try to explain it to the best of your ability.
        
             
        
        
        
Answer:
The difference would be that Mercury has a denser, warmer atmosphere and Earth has a not that dense and gassy atmosphere. The Earth's atmosphere also has a lot of layers while Mercury's doesn't. Those would be the reasons for them both being different. Hope this helped!
Explanation:
 
        
             
        
        
        
The answer is a
Hope this helped
        
                    
             
        
        
        
Answer: C.  Dead snake fossilizing underground. 
A fossil fuel is the fuel that is formed by natural processes, such as anaerobic decomposition of dead plants and animals underground. These organisms and their remains remain deep inside the depth of numerous layers of soil resulting in fuel produced after millions of years. A carbon sink refers to a natural or artificial reservoir that stores and absorbs atmospheric carbon by physical and biological process. The formation of fossil fuel inside the earth is carbon sink.  
Dead snake will be added as a matter on which biological activity called as decomposition will take place. The organic matter of dead snake will be decomposed by microbes in the soil. The organic matter being the source of carbon, after decomposition will become the reservoir of carbon in the form of fossil fuel. 
Therefore, dead snake fossilizing underground is the example of carbon source becoming a carbon sink.