Assertion (A): Diamond and graphite are crystalline allotropes of carbon.

Reason (R): Both diamond and graphite are good conductors of electricity and are used as gems.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): The value of diamond decreases with an increase in the impurities.

Reason (R): Colourless, transparent diamonds are the costliest.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): Carbon dioxide is used in fire extinguishers.

Reason (R): CO₂ gas is a non supporter of combustion, which cuts off the supply of oxygen to fire.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): Carbon monoxide is an extremely poisonous gas.

Reason (R): The gas is formed due to incomplete combustion of carbon.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.