D.<span> A person should seek treatment the first moment he or she suspects having an STI</span>
        
             
        
        
        
Answer:
Its C
Explanation:
Surfactant lowers surface tension at the air-liquid interface and thus prevents alveolar collapse at end-expiration.
 
        
             
        
        
        
Waves of muscular contractions that propel the contents of the digestive tract are called peristalsis.