Помогите пожалуйста1. His German is very poor. He must (study/be studying/have

Помогите пожалуйста
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.