Gel electrophoresis is a technique used to separate DNA fragments according to their size. This is from Khan academy so I believe it is reliable.
 
        
                    
             
        
        
        
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I don’t understand...
Explanation:
You didn’t ask a question ummm
 
        
             
        
        
        
Answer:
Because if the 4-year-old child passes out from holding his breath, he will immediately begin breathing again, keeping him alive.