如图所示,甲、乙之间有四条路可走,那么最短线路的序号是( )
— Sorry, I didn't pass the exam, and then what should I do?
—I think perhaps you should be careful next time.
如图所示,小强正在荡秋千.关于绳上a点和b点的线速度和角速度,下列关系正确的是( )