It takes 8 electrons to fill a shell.
        
                    
             
        
        
        
Two or more organs form together make organ systems.
<u>Explanation:</u>
The basic unit of living organisms is the cell. Multiple cells makes up tissues and tissues make up organs. Two or more organs make up the organ system.
Human body has several organ systems. The organs that make up an organ system can be internal as well as external. Respiratory  system is made up of organs like lungs, nose, pharynx, trachea, diaphragm etc. digestive system is made with organs like liver, small intestine, stomach, mouth , large intestine, pancreas etc.
 
        
             
        
        
        
Answer:
Force = 15.4N
Explanation:
Force=Mass x Acceleration
Force = 20Kg x Acceleration 
20Kg x 0.77m/s = 15.4N
<em>Answer is entirely dependent on what the acceleration is.</em>
 
        
                    
             
        
        
        
Answer:
boiling, freezing, refridgeration, and fertilizer.
Explanation:
the first three have to do with temperature, which tends to kill bacteria. Pesticides kill bacteria by poisoning them