听力原文： I wonder how many of you would went to work in a tall building such as the Empire State Building if you had to climb 102 flights of stairs to reach the top. Not many, I imagine. If it were not for the invention of elevators, or lifts, tall buildings would be unusable.
The first lift was just a box suspended on a rope. Using a series of pulleys, a group of oxen ox strong men would pull the rope end lift the box to a higher point. Lifts were used only for heavy materials, not passengers. Even in the nineteenth century, when steam power was used to operate the lifts, people didn't ride them. They didn't trust the rope that held the box.
In 1853, Elisha G. Otis invented the first safe lift. He showed his invention in New York at the Crystal Palace Exhibition. At the exhibition, Otis was pulled up in an open box that was attached to two guide mils. When he was lifted far above the spectators, he gave the order to cat the rope. To the amazement of the crowd, the lift did not fall straight downward to the floor. Instead, it was held fast to the guide rails by a certain device. He had built powerful metal clamps on the carriage as a safety measure. The demonstration worked, and people have been riding as passengers in elevators ever since.
(26)

A. Disadvantages of tall buildings.
B. Modem elevators.
C. The Crystal Palace Exhibition.
D. The invention of the elevator.