---Is_______ necessary to learn another language?      --- I think so.

 ---Have you found your English book?---No, I haven’t found ________, but I borrowed ________ from Jack this afternoon.

 -- Did you read a book about customs last week?-- Yes, I found ______ very useful to know the customs of foreign countries.

 Are ________ her parents?

---How many children have you got ? ---Two , _______ of them are studying in the university.