题目

When you are ill, you should go to see a doctor. After the doctor looks you over, he will write you a note to take to the chemist for some medicine. Chemists are usually good at reading doctors’ notes. But sometimes doctors write too badly and even the chemist can not read them. One day a woman wrote to a doctor to invite him to have dinner with her family in the restaurant. The doctor wrote an answer, but he wrote too badly and the woman could not read it. “What shall I do?” she asked her husband, “I don’t know whether he is going to come or not. I don’t want to call and sa设x，y满足2x+y≤4x-y≥-1x≤2y+2，则z=x+y的最小值为（　　） A、-8B、-7C、-6D、-5