My favourite shop is called’ Model World’. It is on the second floor of Happy Plaza, near to Pizza Club. It is open from 10 a.m. to 8 p.m. every day.
Model World’ sells all kinds of models. It has model soldiers, cars, boats, airplanes, space shuttles and even dinosaurs. It has models for young children and models for adults (成人). Some models have just about twenty pieces, and others have over 2,000 pieces. You can also buy paints and glue (胶水) and other things there.
The staff at ’ Model World’ is very nice. They are very interested in making models. They will give you advice, and answer all of your questions. The prices are not low but they are not high. My best buy was a model of a helicopter. It cost $ 30 but it had over 400 pieces. It was really fun to make. If you are interested in models, you should visit this shop.

心脏瓣膜只能向一个方向开放，保证了血液流动的方 向是( )

课外阅读。

      1997年早春2月，从英国的爱丁堡传来了小绵羊的阵阵叫唤声，这叫声震惊了世界，人们都将注意力集中到这里。

　　这只名叫“多利”的羊，可不是一只普通的羊，它使人类的一个梦想变成了现实。

　　将一截柳枝插到泥土里，就能长出一棵柳树，将苹果树上的一个芽嫁接到梨树上，就能收获到苹果。植物的这一不用种子发芽就能生长出来的奇特现象，引起了科学家的注意，动物界能不能也这样呢？“多利”就是这项研究的成果。

　　多利天生没有爸爸和妈妈，它是利用动物身上的一个细胞复制出来的，并且它与这个动物一模一样。这完全打破了千古不变的自然规律。科学家把这种技术叫做“克隆”。

　　如今，在科学家的努力下，又出现了“克隆猴”“克隆牛”等等，使这项研究又有了发展。在不久的将来，“克隆”技术必将在医学上广泛运用，从而造福于人类。