A balance is best used to measure a sample's mass.
Answer: C
Explanation:
Weighing balance refers to a measuring instrument which is used to measure the mass of the sample. 
It has two pans. On one pan, the material to be weighed is placed, with adequate known loads on the other one to such an extent that the shaft will be in balance. 
The distinction between the zero perusing and the perusing with the dish stacked demonstrates the contrast between burdens in scale divisions. 
Such an instant weighing needs the arms be of equivalent length.  
 
        
             
        
        
        
heart
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Answer:
Hey ! The number of atoms in the reactants must be equal to the number of atoms in the products so 
CCl4 ~> C + 2 Cl2 
 
        
             
        
        
        
C. Positive Feedback
This is because a response to a stimulus( low blood pressure) acts in the same direction as the stimulus ( even lower blood pressure).
This is opposed to negative feedback where the response would go in the operate direction of the stimulus ( I.e. blood pressure increasing in response to low blood pressure)