简述春秋战国时期的历史大势。

A. cut the casing bands，throw the liferaft over the side，and it will then inflate
B. detach the operating cord，throw the raft over the side，and it will then inflate
C. cut the casing bands，throw the raft over the side，and pull the operating cord
D. throw the liferaft over the side and pull the operating cord

A. 挽救清政府的统治危机
B. 购买和制造洋枪、洋炮镇压农民起义
C. 增强本国的实力
D. 发展资本主义