载重(吨)
4
6
10
12
15
20
运送次数(次)
30
“m>n>0”是“方程mx2+ny2=1表示焦点在y轴上的椭圆”的( )
回忆《陋室铭》,回答问题。
It was c____ that the president would visit China the following month.