【正确答案】
D
【答案解析】[听力原文]
Ladies and Gentlemen, we all know that even with the advances of science and technology in our modern society, it is very difficult for us to predict an earthquake, let alone, prevented. But people had long ago tried every possible means to record and in some way predict the occurrence of an earthquake.
The world"s first instrument for recording earth quakes was invented in China in the second century AD. The instrument, today we would call it a seismoscope was designed by a Chinese astronomer, and geographer called Zhangheng. It was a vessel like device made of bronze and measured in 6 feet in diameter.
Inside the instrument, there was a pendulum that was swing from the movement of a trimmer that is too weak to be felt by a human being. When the pendulum swung, it will pull one of the attached bars. The bar will open the mouth of the dragon sculpture on the outside of the vessel. And a bronze ball will drop, and fall with a clang into the open mouth of a frog sculpture below. This seismoscope could not only record the movement of an earthquake, but also show from which direction the earthquake came.
In AD 138, Zhangheng used his invention to announce that a major earthquake has struck 400 miles northwest of Luoyang, the Chinese capital. His report came long before messengers on horse back brought news of the earthquake to the capital city.
For what purpose was the vessel like seismoscope invented?