A catalyst is a substance which:

The correct answer is Option (4) → Shortens the time taken to reach equilibrium

A catalyst speeds up a reaction without being used up. It provides an alternate pathway with a lower activation energy, and it speeds up the forward and backward reactions to the same extent. The equilibrium position stays the same, but it is reached sooner.

Why the other options are incorrect

Option (1) Supplies energy to the reaction — Incorrect. A catalyst adds no energy; it lowers the activation energy by offering a different reaction path.

Option (2) Increases the equilibrium concentration of the product — Incorrect. Both directions are speeded up equally, so the equilibrium composition does not change.

Option (3) Changes the equilibrium constant of the reaction — Incorrect. A catalyst does not alter ΔG of the reaction, so the equilibrium constant stays the same.

NCERT (2026-27 edition):
3.4.1 Effect of Catalyst – “… It is also found that a catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster, that is, it catalyses the forward as well as the backward reactions to the same extent so that the equilibrium state remains same but is reached earlier.”