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    Which of the following is the hardest substance?
    
    
        
    70. Which of the following is the hardest substance?
    
      - Mercury
 
      - Diamond
 
      - Iron
 
      - Steel
 
    
    Answer
    The correct answer is: B) Diamond
    Explanation
    The hardest naturally occurring substance is known as diamond. This means that the diamond is particularly scratch-resistant.