I think Oxygen is the best answer.
        
                    
             
        
        
        
Answer:
the tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.
 
        
                    
             
        
        
        
Answer:
The correct answer is - O and 6.9; 7.1 and 14
Explanation:
A measuring scale that tells about the acidity or basicity or alkaline nature of a particular object or solution is possible with the help of a pH scale that measures how acidic or basic a solution or object is.
It ranges between 0 to 14. pH less than 7 or ranging from 0.0 to 6.9 is acidic and more than 7 or from 7.1 to 14.0 is basic or alkaline in nature. A measure of the relative amount of H+ ion and OH- ions in water is pH.
 
        
             
        
        
        
A scientist would use, C. Weather Balloon.
        
             
        
        
        
I have a question are you asking what are the molecules of a shark or something