题目

Half an hour of exercise a day can make people live five more years, some health experts(专家) said. They say that walking or riding bikes slowly is good for health. Slow work-outs and even housework every day can make life longer by as much as five years. The news is encouraging （鼓励）lazy people to start taking exercise. “Taking exercise every day has so much help to our health,” said Dr Marc Danzon, “It can stop people from some diseases and becoming fat, and make people strong and mentally (精神上)healthy.” The WHO (世界卫生组织)worries that the public is not关于西北地区河流的叙述，正确的是 [　　] A．黄河是本区惟一的外流河 B．大气降水是本区河流的主要水源 C．额尔齐斯河是本区惟一进入北冰洋的河流 D．本区河流稀少，多为内流河