Основная причина вымирания лебедей?

люди охотятся на них или другие хищные животные

Объяснение:

Ex.24. Open the brackets and use the proper tense (Past Simple, Past Continuous, Past Perfect or Past Perfect Continuous).

1. When he (arrived), I _had beeen__ (living) in London for a week.

2. We _were__ (reading) while he _was___ (eating).

3. When Jack (phoned) me, I __was__ (writing) a letter.

4. When my friend  (came), I had been (doing) an exercise for an hour.

5. The library (had closed) by the time I (got) there .

6. I _was_ (driving) home when I ___ (heard) the news on the radio.

7. They were always having loud parties which went on till the early hours.

8. We _had been_ (walking) for some hours before we  (realized) that we (had lost) our way.

9. No sooner had I  (complained) that I (had not heard) from them for a long time than the letter _ (came).

10. The concert was a great success. When the pianist  (finished) his part, the audience _ (applauded) the orchestra for some minutes.

11. It was the poorest room he had ever (seen).

12. No sooner had she (come) to the station than a fast train from Glasgow (arrived).

13. 6. I _was (driving) home when I  (heard) the news on the radio.

14. I _had_ (finished) my work by afternoon and _was___ (sitting) quietly in my study thinking of the days that _had__ (passed) by.

15. The storm had already (died) away, but very far off the thunder was still (muttering).

1 If I go away on holiday this year, I will swim in the Sea a lot.

2 If I take a suitcase, it will be more comfortable to travel.

3 If I carry a backpack, it will be heavier to move.

4 If I forget to pack my phone charger, I will have to buy a new one.

5 If I arrive late at the airport, I will buy a new ticket.

6 If I fly at night, I will go to the airport by taxi.

7 If I have enough money, I will fly business class.

8 If there is lunch on board, I will have fish with rice.

9 If my flight is delayed, I won't be upset.

Объяснение: