Write the main ideas
of the text in three sentences.
Until the 20th century, constructions of tall buildings were limited because people couldn’t climb up so high and the buildings were made of bricks and stones.
Two major inventions made it possible to build taller buildings, a strong vertical framework of steel beams and safety elevators.
Design problems to build tall buildings are space for elevators and necessity to bring things, air and electricity up and down in, and the safety against strong winds.
Until the 20th century, constructions of tall buildings were limited because people couldn’t climb up so high and the buildings were made of bricks and stones.
Two major inventions made it possible to build taller buildings, a strong vertical framework of steel beams and safety elevators.
Design problems to build tall buildings are space for elevators and necessity to bring things, air and electricity up and down in, and the safety against strong winds.