1. his german is very poor. he must (study/be studying/have studied) very hard. 2. his german is very good, he must (study/be studying/have studied) very hard. 3. his german is considerably improved, ho must (study/be studying/have studied) hard during hi» holiday. 4. he must (study/be studying/have been studying) german these two years, his german is rather rich and fluent. 5. she must (have taken/be -faking/have been taking/ a bath at that moment that's vhy she did not answer your call. 6. she must (be/be being/ have been) at home now, we saw her leaving the office. 7. she must (be/be being/have been) at home, she can't go away because there is no one to look after her sick mother. 8. you must always (think/be thinking/have thought) twice before you say anything. 9. now he must (think/ be thinking/have thought) of what she has said. 10. he knows they are coming. they must (write/be writing/ have written) to him of their arrival in due time. 11. she must (play/be playing/have been playing) the piano now. 12. the foreigner must (understand/understood/have understood) me, for he nodded his head. 13. where is sara? i haven't seen her for a long time. — she must (stay/be staying/have stayed) at her friends'. she wanted to spend july with them. 14. he must (get/be getting/ have got) all he needed, otherwise he would have come again. 15. we must (meet/have met/have been meeting) somewhere before.