The two upper chambers are the atria or auricles. They are the left and right atriums
        
             
        
        
        
Pretty sure the answer is A
        
             
        
        
        
B
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Environment, genetics, selective breeding, random mating, random fertilization, recombination, crossing over, etc
        
             
        
        
        
Answer:
Tell the younger student that organs are singular objects and systems are a group of organs that work together to perform certain jobs.
Explanation:
Organs are singular units that play a part of human survival. (Ex. the heart cleans the blood and pushes through your veins)
Systems are a group of the singular units that work together to perform a certain function.
(Ex. Lungs, heart, veins and arteries make up the circulatory system which transports oxygen, blood, and nutrients through out your body)