Answer:
The energy which is taken by consuming food to perform different functions such as movement, exercise, breathing and thinking etc. 
Explanation: 
The energy from the food is released in the process of respiration. In respiration, energy is released in the form of ATP due to the breakdown of glucose molecules in the mitochondria of the cell. This energy is used by the body in different activities. 
 
        
             
        
        
        
Viruses need to be inside a living thing (of course the living thing has to have the right temperature which most living things do) . When they're inside a living thing they start injecting the host's cells with its DNA in order to make more copies of itself which allows the virus to spread. So basically viruses need to be inside something living.