Answer:
landslide 
This is so easy you can answer this if you study and cheat on class 
 
        
                    
             
        
        
        
Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
 
        
             
        
        
        
Answer:
The answer is 3. Double Helix.
 
        
             
        
        
        
A. punnet square       The punnet square is used to help determine genetic things using the parents as a guide like the color of a rose if something will be tall or short  hope you ask more Qs like this i # luv science. heheheheheh hahahahahaha