(B) K₂SO₄, Na₂SO₄, CaSO₄
These three salts all contain the same negative radical (SO₄²⁻), so they belong to the family of sulphate salts.
The textbook defines a family of salts as salts sharing the same positive or negative radical. Option B has K⁺, Na⁺, and Ca²⁺ as different positive radicals but all share SO₄²⁻ — making them the sulphate family. Option A (NaCl, Na₂SO₄, CaSO₄) mixes chloride and sulphate anions, so it is not a single family. Always check that ALL salts in the option share one common radical.