题干
The children,____ had played the whole day long, were worn out.
A：all of what
B：all of which
C：all of them
D：all of whom
答案(点此获取答案解析）
D
（t≠0）的两条渐近线与直线x＝
围成的三角形区域（包含边界）为D，P（x，y）为D内的一个动点，则目标函数z＝
x－y的最小值为
