When blood is in the lungs, 
where oxygen is plentiful, oxygen easily binds to the first subunit and then quickly fills up the remaining ones. Then, as blood circulates through the body, the oxygen level drops while that of carbon dioxide increases. In this environment, hemoglobin releases its bound oxygen.
        
             
        
        
        
Their skin is thin so they're prone to drying out and they cannot hold moisture in their bodies(Waterproof skin)
        
                    
             
        
        
        
He is correct, the correct answer is 
B. club mosses, horsetails, and ferns.
 
        
                    
             
        
        
        
Answer:
Perception
Explanation:
Perception is usually defined as a collective process of accumulation, selection and interpretation, and organization of the sensory information. In simple words, it helps in the collection of information that is transferred from the different sense organs and interpreted by the brain. This collected information is used in understanding and interacting with the environment.
Thus, perception refers to the use of sense organs such as the nose, ear, eyes and making a person able to smell, hear and see things.
 
        
             
        
        
        
The answer would be 
older peopleshould be vaccinated because elderly individuals are more susceptable to diseases and proper vaccinations can help prevent this matter. some may even think the answer could be antibiotics but antibotics taken repetitively can lose its potency and the body will be immune to its once helpful purpose. hope this helped love