-- Judy's never been late for school, she?
-- . She is always the first to get to school every morning.
A：isn't, Yes
B：Is, Yes
C：has, No
D：hasn't, No
如果实数x,y满足：x-y+1≤0x+y-2≤0x+1≥0，则目标函数z=4x+y的最大值为 ( )
“耒”是传说中神农发明的农具，人们约定俗成地将“耒”作为与农具有关的字的部首。常见的有“耕”(用犁松土)、“耘”(田地除草)、“耦”(两人或两牛并耕)、“耧”(播种工具)等等。通过这些汉字可以了解古代中国的（ ）
