UV rays reacting with the O2 molecules
I might be wrong a little but 
Hope the helps :)
 
        
                    
             
        
        
        
Lightning I think. I don't understand the question
        
                    
             
        
        
        
Answer:
When salt is mixed with water, the salt dissolves because the covalent bonds of water are stronger than the ionic bonds in the salt molecules.
Explanation:
 
        
                    
             
        
        
        
It provides coding for this complementary DNA strand:
     TACTTTCGGATACGTGGT
KEY: adenine goes with thymine (thymine with adenine)
    
         cytosine goes with guanine (guanine with cytosine)