When he ___ the bus , the poor man realized he had left his bag on it.
A:got on
B:got off
C:got to
D:got up
如图为一个草原生态系统食物网示意图,请据图选出一条正确的食物链( )
一位美国历史学家在谈到一战前的欧洲形势时说:“欧洲变成一只‘火药桶’,只等一粒‘火星’将它引爆。”点燃这个“火药桶”的“火星”是( )