题目

Laughter Yoga (瑜伽) is a unique technique invented by Dr Kataria, a doctor from India, by which you can learn to “Laugh for No Reason”. You don’t even need a sense of humor, no funny jokes or comedy programs — just a willingness to laugh — and in the present climate everyone needs to laugh more. Laughter Yoga is a combination of Laughter Exercises and Yogic Breathing, so that you increase the amount of oxygen in your body while being playful, resulting in you feeling healthier, energetic and alive. This actually changes the physical conditions of your body so that you start to fee 设变量x，y满足约束条件则目标函数z＝2x＋y的最小值为 [　　] A． B．12 C．3 D．－3