Answer: C. A substrate
Explanation:
 
A substrate is a substance on which an enzyme act. The enzyme acts on substrate X and converts it to Y.
 
        
             
        
        
        
Answer:
C.  
In general, prokaryotic cells do not have a true nucleus or membrane-bound organelles, whereas eukaryotic cells contain both a nucleus and organelles enclosed by membranes.
Explanation:
 
        
             
        
        
        
The answer is Energy cannot be created nor destroyed.