Answer: i would say the answer is d
 
        
             
        
        
        
Systolic pressure is when the ventricles contract.
        
             
        
        
        
Answer:
The best example of hypothesis which leads to new experiment methods was done by Morgan where he used fruit flies.
 
        
                    
             
        
        
        
Hey There!! 
The answer to this is: C) a factor that may affect an experiment or investigation. This is the best answer. A and B can be eliminated. D describes a controlled variable which is more specific than a scientific variable, thus C is the best answer. It is the best description of just a scientific variable. And, The second one is B: Robert Hooke was a famous scientist who experimented with springs (metal coils). He found that the farther you stretched the spring, the larger the force with which the spring pulled back on you.
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ItsNobody~ ☆
 
        
             
        
        
        
C. It's necessary for the survival of the individual