已知a＞0，实数x，y满足：$\left\{\begin{array}{c}x\ge 1\\ x+y\le 3\\ y\ge a\left(x-3\right)\end{array}\right.$，若z=2x+y的最小值为1，则a=（　　）

去掉小数点后面的零，小数的大小不变．

   Are you a____(健康的) child? Bob, a 14-year-old boy, is very unhealthy. He likes to ____ (乘坐) his father's car to school. Sometimes he goes to school by ____(地铁).  He does exercise only ____ ( 一次) a week. He likes eating ____(垃圾) food very much. This week his parents are in Paris on ____ (度假). So he eats lots of unhealthy food every day. Now Bob is badly____(生病的) in hospital. The doctor says, “ You should ____ （经常）do exercise, and have a good ____(饮食) habits. It's ____ (重要的) for your health.