Câu bị động Giải giúp mình với ạ ----- Nội dung dịch tự động từ ảnh ----- 21. Sarah was writing a letter when I came. 22. They are building a new ring road round the city. 23. The manager must sign the cheque. 24. John will meet me at the airport. 25. They have built a new hospital near the airport. 26. They think that this book is of no use. 27. People believe that he was injured in the accident. 28. They say many people are homeless after the floods. 29. We believe that he is studying painting in America. 30. People think that he knows English well.