The figure shown below demonstrates the solubility curve of a substance. From the statements given below, choose which is/are correct :

P — A is hydrated sodium chloride, B is anhydrous sodium chloride.

Q — A is Glauber's salt, B is sodium sulphate.

R — A is Gypsum, B is calcium sulphate.

1. Only P
2. Only Q
3. Only R
4. Both P and R

Assertion (A): Water is a universal solvent.

Reason (R): Water dissolves all substances except noble metals and glass.

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): A white powder forms on the surface of washing soda crystals which are left exposed to the air.

Reason (R): Washing soda is a hygroscopic substance.

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): A crusty 'boiler scale' is formed in boilers when hard water is used.

Reason (R): Hard water contains bicarbonates of calcium and magnesium.

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.