题目

 Mary worked here as a______secretary and I ended up getting a full-job with the company.    A. pessimistic   B. temporary       C. previous         D. cautious 答案：B如图，目标函数z＝ax－y的可行域为四边形OACB(含边界)，若是该目标函数z＝ax－y的最优解，则a的取值范围是(    ) A．           B． C．          D．