Assertion (A) – True:

Efflorescence appears as a white crystalline deposit on the surface of brickwork. It occurs when water dissolves soluble

salts present in bricks or mortar, carries them to the surface, and then evaporates, leaving the salts behind.

Reason (R) – True:

Burnt clay bricks may contain soluble salts, particularly sulphates of sodium, potassium, magnesium and calcium.

These soluble salts are responsible for the formation of efflorescence during cycles of wetting and drying.

Therefore, both Assertion and Reason are true, and Reason correctly explains the Assertion.