I believe that is ecology
        
             
        
        
        
<h3>Chemical <u>
bond</u> is the answer. </h3>
Explanation:
A chemically bond is defined as the invisible force between two atoms which together forms a molecule. Chemical bonds are of different types - covalent bond and ionic bond. These bonds are formed between the atoms because of a chemical reaction.
In a chemical reaction, different reaction intermediates are formed which leads to the formation of new forces of attraction between nearby atoms or ions to form new bonds. Thus chemical bonds are formed from chemical reaction. 
 
        
        
        
The stem supports the plant and because of the stem the plant is able to grow taller if needed
        
             
        
        
        
<span>The energy of the photon is directly proportional to frequency. 
'cause when frequency increases, it's energy also increases
So, option A is your final answer!
Hope this helps!</span>