Выберите правильный модальный глагол:

1.You ___ work hard at your English if you want to know it. (can, may, must)

2.You feel bad, you ___ see a doctor. (needn’t, should, can)

3. The lights are on. They ___ be at home. (may, must, are to)

4.She ___ to finish school in a year. (may, has, is)

5.I’m afraid the weather ____ change for the worse. (must, may, should)

6.When this scientist was 21 years old he ____ solve a very important mathematical problem. (could, was able to, had to)