Answer is 4 ½ billion.
Scientists think the earth's age is 4 ½ billion. This calculation is based on the radioactive dating. Since the formation of the earth, the time period has been divided into 3 major geological time periods as eon. They are phanerozoic, proterozoic and archean. 
 
        
                    
             
        
        
        
Answer:
D. Strong nuclear force, electrostatic force, weak nuclear force, gravitational force
 
        
             
        
        
        
C.  dim light is <span>the answer
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Answer:
copper is the only material composed of a single pure substance
Explanation:
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