如图是植物根尖结构示意图，请你据图回答：

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    Look, there are some special days in April. April Fool's Day is on April 1^st. Children will have fun on that day. Easter is also in April. There will be an Easter party. Children will play many games. They will roll (滚动)Easter eggs and meet the Easter Bunny. What a happy party! When is the sports meet? It's on 21^st . That will be fun too. Everyone loves April.

填入下面一段文字横线处的语句，最恰当的一句是（    ）

    想想我们的先人，多么富于想象力。一年里中秋的月亮最圆最亮，人们从这又圆又亮的中秋月，联想到人间的团圆及与其相关的平安、健康、和谐，于是凭着自己的一双巧手，做出一种好吃又好看的花糕，中间再放进一点甜甜的馅，表示生活的甜蜜。               。

在实验中通过电路中灯泡的明亮程度来判断电路中电流的大小，这是利用了(    )