Your teacher likes to copy. Found this at https://examples.yourdictionary.com/examples-of-keystone-species.html
Grizzly bears: As predators, bears keep down the numbers of several species, like moose and elk. They also carry and deposit seeds throughout the ecosystem. Bears that eat salmon will leave their dropping and the partially eaten remains that provide nutrients such as sulfur, nitrogen and carbon to the soil.  
 
        
             
        
        
        
Answer:
Viruses use their own catabolic enzymes.
Explanation:
Viruses are the infective particles present in the environment which encloses their genetic material which could be wither RNA or DNA enclosed in the protein coat.
The protein coat is made of the capsomers which are arranged in the tubular structure forming capsid. The viruses do not contain the metabolic machinery of their own that is the reason that they do not have replication or transcription or translation machinery. For this they are dependent on the host organisms as they use their machinery.
Thus, the selected option is correct.
 
        
             
        
        
        
Mitrochondira helps the membrane to save inner plasma
        
                    
             
        
        
        
Reduce your risk of heart failure or also known as heart attack :)) -litliam✨