A:Burning rubbish in the open air.
B:Planting trees in spring.
C:Walking or riding bikes to school.
D:Taking a shopping basket when going shopping.
如图甲是反射弧的模式图,图乙是反射弧中的某一结构.请根据图甲和图乙分析回答下列问题.
如图漫画《中国“结”》主要说明( )