1. That is a pen 
-> That isn't a pen
->Is that a pen ?
2.The book is on the table 
-> The book isn't on the table
->Is the book on the table ?
3.Nam and Ba are very well
-> Nam and Ba aren't very well
-> Are Nam and Ba well ?
4.He is a doctor 
-> He isn't a doctor
-> Is he a doctor ?
5.The children are good students
-> The children aren't good students
->Are the children good students ?