How does salt crystal weathering weaken rocks in desert regions?

Correct answer: Salt forms crystals in cracks and exerts pressure

The direct answer is B, salt forms crystals in cracks and exerts pressure. In dry and semi-dry regions, water containing dissolved salts may enter tiny cracks in a rock. When the water evaporates, salt remains. The salt crystals grow as more salt is deposited, and their growth pushes against the crack walls. Repeated cycles widen the cracks, loosen grains, and weaken or break the rock. Option A is wrong because salt does not melt ordinary rock; melting requires very high temperature. Option B is correct because crystal growth produces mechanical pressure inside cracks. Option C is wrong because salt does not make all minerals magnetic; magnetism is a different physical property. Option D is incomplete and therefore wrong: high salt concentration can affect vegetation, but that is not the mechanism of salt-crystal weathering of rocks. The key chain is evaporation, salt deposition, crystal growth, pressure, and cracking. Memory cue: in deserts, evaporation leaves salt behind; growing crystals push rocks apart.