You want to invite Mr. Williams to give a lecture on "American Literature" in your college. Suppose you are the assistant of the English Department, write a letter and say:

1) the purpose of the invitation;

2) the time of the lecture.

Your letter should be no less than 100 words. You don’t need to write the address. Don’t sign your own name at the end of the letter. Use Ruth instead.

仔细观察下图：请回答： 

（1）1980年我国建立四个经济特区请写出特区名称

    A                           B                          C                       D                               

（2）我国又增开了14个沿海城市，其中E是                     ，F是                          

（3）在图中F处设立了一个开发区，你知道是什么吗？

（4）请说出我国对外开放的目前格局是什么？