predicted that such an event would send ripples(波纹) through space­time.

　　Scientists "heard" the wave with the help of laser beams(激光束) sent through two pipes which form an angle of 90° between each other and are nearly 2，000 miles apart in the U．S.That equipment let them glimpse the nature of black holes.Together they made up the Laser Interferometer Gravitational­Wave Observatory (LIGO)．

　　Gravitational waves were first observed in September 2015 and the second detection(发现) occurred three months later. The third detection, which the astronomers called GW170104, was made on January 4, 2017. The astronomers believed their latest finding "provides clues about the directions in which the black holes are spinning"．

　　"Black holes are beautifully simple. You just need two numbers to describe them completely: mass, how much they bend space­time, and a spin, how much space­time moves about them，" said Dr. Christopher Berry of the University of Birmingham, one of the researchers in the project. "But it takes lots of hard work to measure these from our data. We now have wonderful mass measurements, and are starting to uncover details about the spins of these black holes, which could give evidence for how they formed." The researchers said their discovery added further evidence to support Einstein's general theory of relativity and confirmed the existence of previously unknown black holes.

　　More than 1, 000 scientists from the LIGO Scientific Collaboration were involved in the project along with an additional 280 researchers from the European­based Virgo Collaboration. Scientists hope gravitational waves will offer a completely different view of the universe, allowing them to study events that might be hidden from traditional telescopes. "We have further confirmation of the existence of stellar(恒星的)­mass black holes that are larger than 20 solar masses. We didn't know they existed before LIGO detected them，" MIT researcher David Shoemaker said.

　　【解题导语】　本文是一篇科普说明文。科学家们第三次探测到引力波，相对论再获证实，促进了黑洞研究。

　　5．Who pioneered gravitational waves?

　　A．David Shoemaker. B．Christopher Berry.

　　C．Scientists from LIGO. D．Albert Einstein.

　　D　解析：细节理解题。根据第一段中的"a century after Albert Einstein predicted that such an event would send ripples(波纹) through space­time"可知， 科学家们的这一发现发生在爱因斯坦预测此事件的一个世纪后，因此爱因斯坦是引力波的先行者。

6．How did scientists discover gravitational waves?