How long did Harry spend unloading the supplies?

The answer indicating that Harry spent one hour and a half unloading the supplies is correct because it likely reflects a reasonable and common duration for such a task, especially when considering the volume of supplies and the physical nature of the work involved. Unloading requires not only the physical act of moving items but also involves organization and possibly transporting them to a specific location, which can take additional time.

The other options represent times that might be too short or too specific for the task; one hour could be marginally sufficient depending on the situation, but it might not account for any complications or the need for careful handling. Two hours could be excessive unless there were significant logistics or obstacles. Meanwhile, fifteen minutes is often insufficient for unloading supplies unless they are minimal in quantity, which is unlikely in this context. Overall, a time frame of one hour and a half can accommodate various scenarios that may arise while unloading supplies.