Solution; N:2, H:4, O:3 
Step by step solution:
There are 2 n’s
The 4 after the h means that there’s 4 h
And the 3 after the o means that there’s 3 o
        
                    
             
        
        
        
I would say C. Because babies lungs system is still developing, people with asthmas lungs are week and so are the elderly’s