Answer:
Different brands of nail polishes used by Sarah.
Explanation:
While conducting an experiment two different variables are considered namely dependant variable and independent variable. The variable which is continuously changed to see the effects is called as independent variable and the variable which is being tested is called as dependant variable. 
In the given scenario, Sarah want to know best brand of nail polishes which lasts longest without chipping. Thus the different brands of nail polish used by her is considered as independent variable.
 
        
             
        
        
        
By consuming less than 1200 calories a day it impacts a person’s metabolism by slowing it down and forcing the body to break down its own tissues if it is not receiving sufficient calories to withstand vital functions. There are slight side effects of a less than 1200 calories which are faintness, tiredness, irregular periods, and unsteadiness. Some major side effects might have impact on the gallbladder, gout, excruciating inflammation of the joints and also death.
        
             
        
        
        
The answer is Testicles (testes)