I’m so confused on w’t’f’ you just typed
        
             
        
        
        
Explanation:
Burning fossil fuels, releasing chemicals into the atmosphere, reducing the amount of forest cover, and the rapid expansion of farming, development, and industrial activities are releasing carbon dioxide into the atmosphere and changing the balance of the climate system.
 
        
             
        
        
        
The answer your looking for is c hope it helps 
and #rateme 
        
                    
             
        
        
        
A receptor refers to a protein molecule, which attains chemical signals from external of a cell. The receptor proteins are categorized by their location. On the other hand, the structural proteins refer to the fibrous proteins. One of the essential activity of the structural protein is to maintain the configuration of the cell.  
In the nerve cells, the receptor proteins pick up signals of pain and structural proteins helps in maintaining the shape and configuration of the nerve cell.