An increase in insulating atmospheric gasses (e.g. carbon dioxide)
        
             
        
        
        
Answer:
40% is Adenine.
Explanation:
In DNA, Guanine pairs with Cytosine and Adenine pairs with Thymine.
If a strand of DNA contains 10% Guanine, that means that it also contains 10% Cytosine. 
10% G + 10% C = 20%
100% - 20% = 80% (Adenine and Thymine)
80% ÷ 2 = 40%
The strand of DNA contains 10% Guanine, 10% Cytosine, 40% Adenine, and 40% Thymine.
 
        
             
        
        
        
It's the process of ovulation and menstruation in women and other female primates.