①不断优化投资环境，成为外资投资的最佳选择   

②积极参与国际分工，走出去步伐更加坚定

③不断调整引资结构，利用外资向中高端水平攀升 

④充分利用国际资源，推动开放向提高效益方向转变

    Tom has three good friends. They are Jack, David and Mark. They have different hobbies. Tom likes football. He often plays football on weekends. He thinks playing football can make him strong and healthy. He is in the school football team.

    Jack doesn't like sports. He likes listening to music. He likes Jay Chow best of all the singers. He has many of his CDs. He often listens to music on the way. He thinks music can let him feel happy.

    David doesn't like sports or music. He likes stamps. He collects stamps for five years. The stamps are very beautiful. He thinks collecting stamps can help him know more about the world.

    Mark likes taking photos. He has a few cameras. When he is free, he often takes out his camera and takes some pictures. Some of his pictures are in the newspapers. He thinks the world is beautiful. He wants to show the beauty of the world to others.

把儿歌补充完整。

①圆脸蛋，扎小辫，张大嘴巴____ ____ ____ 。

②大公鸡，____ ____叫，叫我早起上学校。

③村外有只大白鹅，扁扁嘴巴____  ____ ____。

等差数列{a_n}的前n项为S_n，若公差d=﹣2，S₃=21，则当S_n取得最大值时，n的值为（　　）

依次填入下列各句横线处的词语，恰当的一项是(    )

①面对人类，失去_____ 之心的医学是冰冷的，有缺陷的。

②只要是那些彰显正义、美德，代表了先进文明的人，都有_____ 得到树碑的殊荣。

③沙丘上独行的山狮，虽然没有动作，没有吼声，但仍能使人感觉到那股潜在_____

④国庆节前夕，党和国家领导人在人民大会堂举行盛大宴会，_____ 各国贵宾。