In mammals, the powerful muscle that aids in breathing is the diaphragm. This muscle expands and contracts the chest cavity and forces air in and out of the lungs.
Hope that helped =)
        
                    
             
        
        
        
Answer:
The correct answer is "change".
Explanation:
The missing options of this question are:
A. natural selection.
B. immutability.
C. survival of the fittest.
D. change.
The correct answer is option D. "change".
The scientific racism that was prevalent during Charles Darwin books publications was related to the concept of "pure races", and the association of the inheritance of the "superior attributes" related to these races. Darwin's ideas were incompatible to this scientific racism, since Charle Darwin theories support the idea of a constant change among all people attributes, produced by genetics behavior and exposure to environmental factors. 
 
        
             
        
        
        
The answer would be, if I understand correctly, skeletal and smooth muscle tissue both help the body move, and give the body form. The skeletal structure give the body structure, and the muscles help the body move.