科学家们发现，星系的光谱向长波方向偏移，称之为____ ，这一现象说明____ ．

元朝是我国第一个统一全国的少数民族政权,下列事件发生在元朝的是  (    )

①铁木真统一蒙古 ②马可·波罗来华

③回族形成   ④经济重心南移完成

⑤建立行省制度

   The world is divided into two parts. One half of the world is rich and 1is poor. In the poor part, a lot of people have2got enough to eat. When they are ill, none of the3can receive them because they have no money. In the rich 4, people eat very well, 5 a dog or a cat in North America eats   6than a child in poorer countries.
   The poor countries have some difficult problems. Sometimes the land is too poor to grow7on. People there have 8rich land nor enough water. The land9be made better, but a lot of things must be done. The people must be taught and water must10.
   But rich countries have problems, too. There are not always good places to 11. Sometimes the air is not clean and the rivers are too 12to swim in or to drink. The roads and streets are full of people and cars. Cars and buses have to move 13. Noise is too much. Some people have no houses to live in. Something must be done about these problems. The air and the rivers must be cleaned and be 14clean. More houses have to be built. 15these things cannot be done easily.

提示词：fail, unhappy, spend ……on, talk with……, do sports, learn to smile, believe……

Dear Li Hua,

    ……

Yours,

Tom