A：草→羊→狼
B：阳光→草→昆虫→蛙
C：兔→狐→细菌
D：草→兔→狼→细菌
周日有一节舞蹈课。
There is ____ ____ ____ on Sunday.
氮气化学性质稳定的原因是 （ ）
A. north B. for his trip C. in the future D. sour lemons E. school uniforms F. go to the park
