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.

某小区最近一段时间由于楼道灯的供电系统电压偏高，所用的路灯“220V40W”灯丝经常熔断，在电压暂时无法改变的情况下，为了延长楼道灯的使用寿命，小明所采取的下列方法切实可行的是：

读我国某区域土地利用类型面积变化图（如图），回答以下问题。

下列各句中，划线虚词使用恰当的一句是（   ）