1 . The noise and the smell of smoke made it impossible for me to c________ on my work in the office yesterday morning.

2 . 用所给动词的正确形式填空。

ring, examine, shut, concentrate, make an effort

1. The door ________ by the wind just now.
2. —Marc, where is Kevin?
—He ________ his motorcycle. It doesn’t work.
3. My brother ________ to stay healthy since he entered the university.
4. He ________ on his schoolwork if he is allowed to practice running after school.
5. The bell ________ and everybody is in the classroom.