Подчеркните в предложениях модальные глаголы или их эквиваленты.1.One theory is that Stonehenge was a place from where stars and planets could be observed.2.Tourists are to arrive on Monday.3.Living with them he has to follow their rules.4.You will have to be at the airport at three o"clock.5.Government intervention may be necessary from time to time.