Are these your books 　— No, they aren’t. They are ____________.

Our city used to be beautiful.—That’s true. But _________ there is too much pollution. It’s not as beautiful as before.

Is this the reason ___ at the meeting for his carelessness in his work?

It’s important _________ us _________ some goodfriends.

It is only by practising English for several hours every day _________ be able to use it freely.