I think it's A not sure tho
        
             
        
        
        
Answer: The virus weakens as time passes.
Explanation:  The virus will weaken continuously during transmission, and  will reduce its toxicity after several generations of transmission, without causing much harm to the human body. 
 
        
             
        
        
        
Answer:
The energy comes from electrons produced by oxidation of biological molecules.
Explanation: In photosynthesis, the energy comes from the light of the sun. 
Hope this helped! :)