What should you order if your fuel oil tank has 10,000 gallons remaining and the tank capacity is 20,000 gallons?

The appropriate order in this scenario is to request 10,000 gallons of fuel oil. The fuel oil tank's total capacity is 20,000 gallons, and currently, there are 10,000 gallons left. To reach full capacity, it is necessary to fill the tank from its current level back to 20,000 gallons.

Since the tank holds a maximum of 20,000 gallons and has 10,000 gallons remaining, adding another 10,000 gallons will restore it to its full capacity. Other options would not adequately fill the tank, leaving it short of what is required, or would exceed its capacity if a larger amount were ordered. Thus, the best choice to effectively utilize the tank is to refill it with the full amount needed to reach its limit.