Answer:
A 40 percent
Explanation:
If guanine is 10 percent this means that cytosine will also be 10.thats a total of 20 percent. We will then have 80 percent remaining for thymine and adenine. As we know adenine make a bond with thymine so 80 divide by 2 is 40 percent for each 
 
        
             
        
        
        
The answer is going to be C
        
                    
             
        
        
        
A because protons make the atom the element it is and the molar mass is made up by the neutrons and protons. The protons must stay the same to keep the same element and electrons hardly have mass so A