A:which; whe
B:that; that
C:where; that
D:where; which
亚洲绝大部分位于
若x, y满足约束条件x-1≥0x-y≤0x+y-4≤0,则yx的最大值为____ .
被俄罗斯人誉为“母亲河”的是( )