做曲线运动的物体，在其轨迹上某一点的加速度方向（   ）

   Some people don’t like doing sports because they think it is hard work and will make____ (他们) feel tired . That’s wrong! Sports help us to____ (保持)healthy , happy and live longer .If you____ (从不) do sports , you will get unhealthy easily . Sports are____ (也)a good way to make friends .People from different____ (地方) may not know each other , but after a game , they often become good friends .And sports in winter and ____ (夏天)are not the same.____ __(swim) is fun in hot weather , while skiing is great____ cold days . Many people____ (享受) watching others play games .They often get very____ (兴奋) when “their” players or teams win .

依次填入下面句子横线处的词语，最恰当的一项是（   ）
作为改革开放和现代化建设的总设计师，他的名字     ，在建设有中国特色社会主义理论中,他的文艺思想是十分重要的构成部分。他在论及文艺问题时，不是就文艺论文艺，而是把它放在国内、国际两个大局的时代天平上进行全方位    ，因而体现出了     、宏观把握的气势和特点。

极昼现象从北极点扩大到北极圈的时期是（　　）