已知x、y为正实数，且2x+8y-xy=0，求x+y的最小值（ ）。
18
同义句转换。
1. After they arrived , the students welcomed them.
The students welcomed them ________ ________ ________ they arrived.
2. John uses his own words to tell us.
John ________ us ________ his________ ________.
3. We booked a room for our holidays.
We ________ ________ ________ a room for our holidays .
陇海线与京广线交会的铁路枢纽是（ ）
A．石家庄
B．郑州
C．武汉
D．广州
