1. A. Scientists | B. Dentists | C. Doctors | D. Participants |
2. A. swim | B. swims | C. swimmers | D. swimming |
3. A. must | B. have to | C. need | D. A & B |
4. A. remember | B. forget | C. think | D. believe |
5. A. swim | B. To swim | C. swimming | D. B & C |
6. A. difficult | B. difficulty | C. different | D. differently |
7. A. ought | B. should | C. need | D. will |
8. A. learn | B. to learn | C. learning | D. to learning |