1 . 写出下列句中动词ing的作用
1. Walking in the park, she saw an old friend.
2. Being ill, he couldn’t go to school.
3. Working hard, you’ll make great progress.
4. The boy ran even faster, reaching the school out of breath.
5. All night long he was awake, thinking of the problem.
6. Is there a swimming pool in your school？
7. The bridge being built now will be the longest one in the world.
8. He heard the song being sung next door.

2 . To some,happiness is_________________________.(根据句意填空)