Ex 3.
1 have been studying
2 hasn't been playing
3 Has it rained
Ex 4.
1 It has started
2 had became
3 I have lost
Ex 5.
1) I haven't known ... Do you have any ideas?
Have you been to Egypt? I went there last spring.
No, I have never visited Egypt before.
2) What did you do last weekend?
I spent the weekend in London. And I have just returned.
Oh, I have never been to London.
It was fantastic.