Yes the answer is genes.
Polygenic traits are determined by multiple gene received from each parent. 
        
             
        
        
        
Smith is pursuing an ekg technician certification program. He will be one of the healthcare professionals referred to as cardiovascular technologists and technicians. They help monitor heart health on a broader level.
        
                    
             
        
        
        
Answer should be A if multiple choice
 
        
                    
             
        
        
        
Answer:
The options are
Complex
Identical 
Inconsistent 
Non-testable
The Answer is Identical 
Explanation:
The groups of scientists in different parts of the world who are dating fossils found in a rock layer of the same geologic time period. The findings have to have some common characteristics which links it to being in the same geologic time period. 
This however validates the fossils having to be identical to match those found in other parts of the world.
 
        
             
        
        
        
Skeletal muscle is under voluntary control