There are forty-eight students in our class. There are twenty-three boys and twenty-five girls. Some students live near the school, and some others live very far from the school. About half of the students come to school by bike. They often get to school at a quarter to seven. About ten students often come to school by bus. They often go to school very early, too. Another ten students come to school on foot. Their homes are near the school, but they are often late for school, because they get up very late.

— Listening to music.  

世界卫生组织驻华代表说：虽然世界各国的卫生体系都在变革，但是中国的医改步伐超过了任何一个国家。我国加快推进医疗制度改革，这体现了（  ）

读等高线示意图，已知a>b。回答问题。