Correct Answer: when only the price of the commodity change

Solution : The correct answer is when only the price of the commodity change.

If the price of the product changes, the demand curve will not vary. When a good's price changes, it creates a movement along the demand curve rather than a shift in the curve. Any additional factor will cause the demand curve to move to the left or right. For instance, if consumer income rises, buyers will be able to purchase more things, shifting the demand curve to the right. When the price of an alternative item falls, individuals are more inclined to purchase it, shifting the demand curve to the left.