In building new bridges, they must solve many different problems. чем является слово building в предложении?

In mid 1997 film critics insisted that the new Titanic film (was) a flop. The director, James Cameron, however, thought differently. Originally, the studios wanted Matther McConaughey to play Jack, but Cameron (insisted on having) Leonardo DiCaprio, who was perfect for the role. Then Cameron complained that Celine Dion's song (was) too sentimental and (refused to include) it. But James Horner, who wrote the film score, (persuaded him to use) it.When several stunt people were injured during filming, critics (accused Cameron of being) ruthless and criticised him for putting people's lives in danger. When the film finally opened in December, critics still (warned filmgoers it was) a disaster. Four month later, Titanic won eleven Oscars. Everybody (congratulated Cameron on making) such a marvellous film, which earned nearly two billion dollars. But some critics never (admited making) a mistake.

1.If you tell the truth, you will feel sorry about it.
2. If you learn the words, you won't get a bad mark.
3. If Tony has a ball, he will play a game.
4. If I were a diplomat, I would travel a lot.
5. If I listen to the radio, I will know all the news.
Conditional II.
6. If he found her telephone number, he would phone her.
7. If I heard the noise, I would open the door.
8. If Helen had the information, she would tell them everything.
9. If she felt well, she would go to the mountains.
10. If I had more money, I would buy the computer.
Conditional III.
11. If he had waited, he would have met them.
12. If we had learnt the words, we would have had a 5 for the dictation.
13. If I had known Italian, I would have visited Italy.
14. If I had lived near the river, I would have gone swimming every day.
15. If you had worked hard, you would have got the job.