Когда употребляется some, а когда any?

 We use some in affirmative and we use any in negative and interrogative sentences.

There are some birds in the cage.

There aren’t any birds in the cage.

Are there any birds in the cage?

He has bought some interesting books.

He hasn’t bought any interesting books.

 Has he bought any interesting books?

Mary has seen some interesting pictures.

Mary hasn’t seen any interesting pictures.

Has Mary seen any interesting pictures?

He wants to buy some presents for his friends.

He doesn’t want to buy any presents for his friends.

Does he want to buy any presents for his friends?