Answer:
Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. As the atrium contracts, blood flows from your right atrium into your right ventricle through the open tricuspid valve.
Explanation:
 
        
             
        
        
        
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 -The mutation could make it easier for an organism to obtain food.
-yes, a correct anwer!
 -The mutation could make an organism need more food.
-no, this would make it harder for the organism to survive
 -The mutation could improve the organism's sight.
-yes! better sight means more information, which is beneficial
 - The mutation could let the organism run faster.
-running faster means advantage over pray and predator - also a correct answer
so all are correct except on the second one. 
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Answer:
 b concentration insid e and out side the cell
 
        
                    
             
        
        
        
Answer: absolute certainty is often difficult to achieve. Scientific uncertainty generally means that there is a range of possible values within which the true value of the measurement lies. 
Please brainliest
 
        
             
        
        
        
Answer:
During meiosis, an event known as chromosomal crossing over sometimes occurs as a part of recombination. In this process, a region of one chromosome is exchanged for a region of another chromosome, thereby producing unique chromosomal combinations that further divide into haploid daughter cells.