11. Which is the rarest naturally occurring element of earth?

1. 1. Gold

   
   
   

   2. Antimony

   
   
   

   3. Germanium

   
   
   

   4. Astatine

   
   
   

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1. View Hint View Answer Discuss in Forum

   It is a radioactive element.

   Correct Option: D

   It is a radioactive element.

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12. The deficiency of which one of the following leads to dental caries?

1. 1. Iron

   
   
   

   2. Copper

   
   
   

   3. Fluorine

   
   
   

   4. Zinc

   
   
   

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1. View Hint View Answer Discuss in Forum

   Fluorine

   Correct Option: C

   Fluorine

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13. Which among the following is an element?

1. 1. Alumina

   
   
   

   2. Brass

   
   
   

   3. Graphite

   
   
   

   4. Silica

   
   
   

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1. View Hint View Answer Discuss in Forum

   Graphite is an allotrope of carbon. Alumina (Al₂O₃) and silica (SiO₂) are oxides and Brass is an alloy of Cu and Zn.

   Correct Option: C

   Graphite is an allotrope of carbon. Alumina (Al₂O₃) and silica (SiO₂) are oxides and Brass is an alloy of Cu and Zn.

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14. Which one of the following elements exists in liquid state at room temperature ?

1. 1. Mercury

   
   
   

   2. Lead

   
   
   

   3. Sodium

   
   
   

   4. Calcium

   
   
   

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1. View Hint View Answer Discuss in Forum

   Mercury exists in liquid state at room temperature.

   Correct Option: A

   Mercury exists in liquid state at room temperature.

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15. Carborundum is a compound of

1. 1. Ca

   
   
   

   2. Ge

   
   
   

   3. Si

   
   
   

   4. S

   
   
   

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1. View Hint View Answer Discuss in Forum

   Carborundum is silicon carbide.

   Correct Option: C

   Carborundum is silicon carbide.

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