Помогите вставить модальный глагол

1.  George has travelled a lot. He can/may speak five foreign languages.

2. To become a specialist one must/needs to get proper training.

3. Prison officers have/ought to work under stress.

4. I’m afraid I can/can’t participate in the scientific activities.

1. George traveled a lot. He can speak five foreign languages.

2. To become a specialist, you need to undergo appropriate training.

3. Prison staff must work under stress.

4. I'm afraid I can't participate in scientific activities.