1. ---Hi, I'm Peter. Are you new here? I haven't seen you around.

---Hello, Peter. I'm Bob. I just ________ on Monday.

     A. start               B. have started   C. started        D. had started

2. Susan had quit her well-paid job and ________ as a volunteer in the neighborhood when I visited her last year.

     A. is working          B. was working    C. has worked    D. had worked

3. China's high-speed railways ________ from 9,000 to 25,000 kilometers in the past
few years.

     A. are growing         B. have grown     C. will grow¡¡¡¡  D. had grown