Assertion (A): Carbon can form a large number of compounds, most of which are studied under organic chemistry.

Reason (R): Carbon atoms can form long chains with each other.

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): Coal is used as a fuel for domestic purposes and industries.

Reason (R): Coal is an amorphous form 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.

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): Pencil leads are made up of graphite.

Reason (R): Graphite leaves a black mark on paper.

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.