问题详情

We can infer from the passage that ______.
A．before the Civil War, the Northern states needed more slaves to work for them
B．after the Civil War, there was a strong hatred from the Northern states against the Southern states
C．before the Civil War, the Northern states had a better economic system than the Southern states
D．before the Civil War, the Northern states had an economic system different from the Southern states请帮忙给出正确答案和分析，谢谢！