Ide say c is the best option here but i wouldent bank on my answer.
        
             
        
        
        
Natural selection is a type of evolution that allows organisms to adapt into the environment they're in for survival. 
        
             
        
        
        
Answer:
A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. To do this, certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are called antigens, and they are present on all viruses and bacteria
Explanation:
 
        
             
        
        
        
Do you have options to pick from
        
             
        
        
        
1. Air enters the nostrils.
2. Air passes from the trachea to the bronchi
3. Air diffuses from the alveoli to the blood cells.
4. Oxygen enters the blood cells.
5. Blood transports oxygen to other cells.