C
If you gaze（凝视）through a telescope at a distant galaxy（星系）, it may glow brightly with the light of hundreds of millions of stars. Despite（尽管，不顾） all that light, most scientists think that at the center of a big galaxy lies something very dark: a black hole. A black hole is a region of space with gravity so strong that nothing can escape, not even light.
Astronomers recently announced they had observed a faraway galaxy that may have at its center two black holes, very close together. Based on their observations, the stargazers suspect one of the black holes has more mass than the other. The more mass something has, the stronger its gravitational force, so a larger black hole has a stronger gravitational attraction. The smaller black hole orbits（作轨道运行） the larger black hole, just as the earth orbits the sun.
The biggest galaxies in the universe form when two smaller galaxies collide（碰撞）. If two galaxies merge（合并）, then all of their stars start orbiting a common center. The black holes at the galaxies’ centers should come together, too. Galaxies are colliding all the time, so we should be able to find lots of black hole pairs. But that’s easier said than done—astronomers rarely find these in deep space.
To find a black hole is complicated. A black hole doesn’t produce any light, so how can you find one in space? Astronomers think when something (like dust) falls into a giant black hole, a jet of radiation, a form of energy, may stream away. If this radiation is strong enough, it forms a quasar（类星体）.
The Arizona astronomers looked at more than 17,000 quasars and finally found a galaxy that may have a double black hole at its heart. Though the finding of their research is still unconfirmed, and they may be mistaken, the truth will be revealed in the future.
63. Which of the following is TRUE about black holes?
A. A black hole is a region in galaxies with nothing in it, even a bunch of light.
B. Black holes are used by astronomers to study how quasars come into being.
C. When different galaxies meet in space, the black holes become bigger and bigger
D. Some scientists think there’s one black hole in a galaxy, but others think there’re two.
64. From the second paragraph we can infer that ________.
A. a larger black hole pushes a smaller black hole away
B. a larger black hole pulls a smaller black hole toward it
C. the places of black holes are fixed, so we can see them clearly
D. a smaller black hole moves around a larger one because of radiation
65. According to the passage, astronomers think that there should be many black hole pairs because____________.
A. a black hole can produce light
B. black holes can attract one another
C. different black hole pairs come into being with the meeting of galaxies.
D. a big black hole can usually be divided into two small black holes
的离心率为
椭圆与x轴交于两点A(a，0)、B(-a，0)，过点C的直线l与椭圆交于另一点D，并与x轴交于点P，直线AC与直线BD交于点Q。
为定值。
，代入椭圆方程得(4k2+1)x2+8kx=0。
，代入直线l的方程得y1=1，
，又直线BD的方程为
联立得
