In this section, you will hear several passages. Listen to the passages carefully and then answer the questions that follow. Questions 11 to 13 are based on the following passage. At the end of the passage, you will be given 15 seconds to answer the questions. Now listen to the passage. What does the professor mainly discuss
A. The development of the modern skyscraper.
B. The skyscraper’s effect on urban areas.
C. Problems with future skyscraper construction.
D. Safety regulations for skyscraper design.