We may learn from the passage that ______.A．people do not care about the removal of barrie

We may learn from the passage that ______.

A．people do not care about the removal of barriers between countries

B．people can not remove the obstacles made by themselves

C．man-made barriers are sometimes harder to overcome than natural ones

D．barriers should be taken for granted as they always exist

请帮忙给出正确答案和分析，谢谢！