Объяснение:
1. Because it was very difficult to build tall skyscrapers at that time and it was dangerous,it was difficult to get the necessary funds to build a skyscraper.
2. They can start building skyscrapers when they are sure that they have the right materials and the land is suitable for building a tall building.
3. When the Elevator was invented, people's lives became noticeably easier.And people were able to build taller skyscrapers.
4. Because it would be inconvenient to build them outside the city, especially since when building a skyscraper in the city there may be offices,shops,apartments, etc.
5. Because these buildings are built "to the sky".
6. It was built over two years, from 1929 to 1931.
7. Here you can find various cafes, shops, supermarkets and apartments, as well as much more.
2 can`t they
3 didn`t they
4 will you
5 did they