If the quantity of rice bought decreases from 250 tonnes to 200 tonnes owing to a 2% rise in price, it shows that there is a change in

The change described in the question shows a change in quantity demanded. Quantity demanded refers to the amount of a good or service that consumers are willing and able to purchase at a given price, while all other factors remain constant. In this case, we are told that the price of rice has increased by 2%, which would lead to a decrease in the quantity demanded of rice. This is because consumers may find rice to be relatively more expensive compared to other substitutes, and therefore may choose to buy less rice. We are also given information that the quantity of rice bought has decreased from 250 tonnes to 200 tonnes. This further confirms that there has been a change in the quantity demanded of rice. Therefore, we can conclude that the change described in the question shows a change in quantity demanded, and not consumers' income, demand, or consumers' tastes.