Thanks to better health care, most people are living ____ (healthy) and longer lives. Someone who is born today can expect to live about thirty-five years longer than someone who ____ (be)  born in the nineteenth century. Here are five ____ (rule) for a healthy life.

    First. Doctors say you should get off the sofa. To keep fit, you have to walk ____介词) least 10, 000 steps every day. In the past, people's jobs required more physical effort. They often____ (have) to walk for miles every day. When farmers were ____ (work) in the fields, they were keeping fit at____(冠词) same time.

    Second. Rest while you can! When we were babies, we ____(sleep) for much of the night. Teenagers do not need as much sleep as babies, but it is important for you to get about eight ____ (hour) sleep a night. At weekends, you have ____ (get) more time, so use it not just for your friends, but for rest too.

面对洪灾，一位东北网友在微博上说：“洪水可以摧毁家园，却摧不毁我们战胜困难的信心和意志。因为我们有着共有的信念──克服困难，走出困境，重建家园！”这体现了以          为核心的中华民族精神。 (     )