测定电源的电动势和内阻的实验电路如图所示，请回答下列问题：
---It's everyone's duty to join the Clean Your Plate Compaign(光盘行动).
---Sure, we should try to all the food that we have ordered.
下列是几种粒子的结构示意图，请你仔细观察并回答问题：
