Измените каждое предложение, поставив модальные глаголы в сказуемом в прошедшее и

1. Не must work hard to finish his experiment. - Не had to work hard to finish his experiment. - Не will have to work hard to finish his experiment.
2. I can devote myself to scientific work. - I could devote myself to scientific work. - I will be able to devote myself to scientific work.
3. They may carry out these experiments at the laboratory. - They were allowed to carry out these experiments at the laboratory. - They will be allowed to carry out these experiments at the laboratory.
4. She can study chemistry at the university. - She could study chemistry at the university. - She will be able to study chemistry at the university.