西方学者李普曼在其《道德序论》中指出：“在近代，人们已发明了作出发明的方法，人们已发现了作出发现的方法。机械的进步不再是碰巧的、偶然的，而成为有系统的、渐增的过程。”这说明

阅读理解

                                                                                      (B)

    Long long ago, there was no paper in the world. People had to write characters(汉字) in bamboo slips or stones.Then there was a man named Cai Lun who was a Chinese man. He made people use all kinds of things to invent paper. From then on, people can use paper to write on. Paper is a great invention. We always remember the great inventor Cai Lun. Nowadays paper is very useful in our work, study and our life. It really means a lot to human beings.

根据短文内容，判断下列句子的正 (A)与误 (B)，并在答题卡的相应位置将其涂黑。

设变量$x,y$满足约束条件$\left\{\begin{array}{c}y\ge 0\\ x-y+1\ge 0\\ x+y-3\le 0\end{array}\right.$$\begin{array}{c}\mathrm{}\\ \mathrm{}\mathrm{}\\ \mathrm{}\mathrm{}\end{array}$，则$z=2x+y$的最大值为  (    )