Ⅰ. 用所给词的正确形式填空
1. Mary entered the office, ________ (sit) at her desk and began to type the letter.
2. The Smiths ________ (have) breakfast when he came in.
3. The young girl sitting next to me on the plane was very nervous. She ________ (not fly) before.
4. I ________ (go) along the street looking for a parking space to park when the accident ________ (occur).
5. I ________ (meet) an old friend of mine in the street yesterday.
