When plotting two or more curves, we need a key or legend to distinguish them.
当绘制两条或多条曲线时，我们需要关键字或图例来对它们进行区分。
2
By looking at the legend (or key), you should be able to tell which line in the graph is which.
通过查看图例(或键)，您应该能够知道图中的线分别是何种曲线。
3
Jie Zitui is generally accepted as the leading role in the legend derived from Qingming Festival, but now he is considered as a key figure related to the origin of the Dragon Boat Festival.