Помогите пожалуйста определить какой частью речи в предложении является герундий.
1. What is the reason for his having left our city so suddenly?
2. We heard of the experiment having been started last week.
3. He improved his report by changing the end.
5. They objected to his staying at home.
6. Instead of restoring the old theatre they decided to built a new one in the centre of the town.
7. New possibilities for applying atomic energy open up.
8. It is possible to set up power stations based on utilizing the heart of the Sun.
9. The idea of creating a multi-stage rocket belongs to Tsiolkovsky.