Final answer:
The best extension cord for connecting an appliance at least 10-12 yards away from a wall receptacle is option (d) one 50 foot #10 cord, due to its lower resistance which means less voltage drop and more efficient power transmission.
Step-by-step explanation:
The goal is to choose the best extension cord for reaching from a wall receptacle to a store display which is 10-12 yards away. The most suitable extension cord must handle voltage drops well and provide adequate power to any appliances used with it. If an extension cord with too high resistance (such as an #18 gauge cord) is used, there will be a significant voltage drop across it, leading to a decrease in both voltage and power available to the appliance, hindering its performance as per the information provided. So, a cord with lower resistance is preferable.
The best option among the choices given would be (d) one 50 foot #10 cord, as the larger wire gauge (lower number) indicates a thicker wire, which has less resistance. The #10 gauge cord would lead to a lower voltage drop compared to an #18 or #16 gauge cord, allowing the appliance to receive more of the power and operate effectively.
The options provided suggest using a single long cord rather than connecting two shorter cords, because additional connections can introduce more points of resistance. The thickness of the wire is indicated by the gauge number, and a lower gauge means a thicker wire, which is less resistant and thereby more efficient for longer distances and higher currents.