Mixture and alligation basics – UGC NET Question

Statement A correctly describes the overall concentration as a weighted average of component concentrations. Statement B is a special case for equal quantities, where the weights are equal and the average is arithmetic. Statement C states the classical alligation rule connecting mixing ratio to the differences from the mean. Statement D is false because adding pure water does not change the solute amount, and E is false since diluting with water lowers concentration but does not decrease the amount of solute. Hence A, B and C only are correct, which corresponds to option A.

Option A:
Option A is correct because it includes the general weighted-average idea, its equal-quantity special case and the alligation rule, while excluding D and E, which misunderstand how solute amount changes under dilution.

Option B:
Option B is incorrect since it includes D, which wrongly asserts that adding pure water increases solute amount, mixing an error with accurate statements.

Option C:
Option C is wrong because it includes E (false: adding water alone does not reduce solute amount) and omits B (true equal-quantity averaging), so it does not match the true set.

Option D:
Option D is incorrect as it contains D (false) and omits A (the key weighted-average principle), making it both incorrect and incomplete.