I believe the answer is B
        
                    
             
        
        
        
The answer is B: P
in which the P stands for Parent generation 
hope this helped!
p.s. if you found this helpful please mark my answer as brainliest! it would mean a lot to me, thanks!
        
                    
             
        
        
        
A testable question is a question that can be answered and solved by creating and conducting an experiment. Testable questions are often about changing one item to see what impact it has on another.
Example:
Does changing the height of the ramp affect the speed of the skateboard going down the ramp?
        
             
        
        
        
What can u explain more ur question
        
                    
             
        
        
        
Answer:
Genes involved in making enzymes to breakdown lactose.