一． 单项选择（共15小题，计15分）：请从每个小题的四个选项中，选出一个最佳答案。
（ ）1. ______ the boy was walking down the street, the UFO landed.
A. While B. After C. As D. Before
（ ）2. You must run quickly . The train ______in two minutes .
A. go B. went C. will go D.goes
（ ）3.____people lost their lives in the earthquake
A. Hundred of B.Hundreds of
C. Hundred D. Hundreds
（ ）4. Mary ___________ computer science last year.
A .studies B. studied C. will study D. is studying
