Extension of supply occurs due to change in ______.

Own price of the commodity.

The correct answer is Option (1) → Own price of the commodity.

Extension of supply refers to an increase in the quantity supplied of a commodity due to a rise in its own price, assuming other factors remain constant (ceteris paribus). It is shown as a movement along the supply curve, not a shift of the curve.

Other factors like the goal of the firm, technique of production, and number of firms cause a shift in the supply curve, not extension.