Answer:
b
Explanation:
The answer is B becuase "where do people buy tools is not a scientific question, and neither is C.
 
        
                    
             
        
        
        
C: from what I can see in the graph
        
             
        
        
        
Explanation:
The enzyme is unchanged so that, it can be reused when more substrate is available. 
to know more ,enzymes about Biological Catalyst that are used to speed up the rate of a biological reaction but are not used up at the end of the reaction