8. Goods are __________ as long as they are returned in good condition. (change)

The correct answer to fill in the blank is "exchangeable."

In this context, the word "exchangeable" describes goods that can be swapped or exchanged for other goods, typically under certain conditions. The phrase "as long as they are returned in good condition" indicates that the goods must be in a satisfactory state for them to be eligible for exchange. This typically applies in retail settings where return policies allow customers to return items for a different size, color, or even a complete refund if the item is not damaged or used improperly.

The root word, "change," relates directly to the idea of exchanging items, but in this case, the adjective form "exchangeable" is more appropriate because it specifies the condition under which the exchange can happen.

Thus, the completed sentence is: "Goods are exchangeable as long as they are returned in good condition."