Answer:
C
Explanation:
it should be all of them really but c and d are the best options so I would go with c
a control group is making an observation
 
        
                    
             
        
        
        
Step-by-step explanation: Each angular point of a polygon, polyhedron, or any other figures such as squares, triangles, etc is a vertices. A vertices is simply an angular point in any figure.