北极圈穿过亚洲的三条河流是: 、 、 。
鄂毕河、叶尼塞河、勒拿河
—Do you think he will do me a favor?
— As far as I know, he is the last one to help others. He______be prepared to give you a hand, though.
A.might
B.must
C.can
D.should
以人民币为例,阐述汇率变动对一国经济的影响。