题目内容：

And then there were nine

The past two decades have seen astronomers’ catalogue of planets expand over two hundred times, as new techniques and better telescopes have found more than 2,000 of them orbiting stars other than the sun. But in the solar system itself, the list of planets has actually shrunk, Pluto（冥王星）having been downgraded from that status in 2006. The number of the sun’s planetary companions has thus fallen from nine to eight.

Now, a pair of astronomers from the California Institute of Technology think they have evidence that will restore the sun’s record to its previous value. Their analysis of objects orbiting in the Kuiper Belt（柯伊伯带）, a ring of frozen asteroids（小行星）that circle beyond the orbit of Neptune (and of which Pluto is now regarded as the largest member), suggests to them that something about ten times as massive as Earth has changed those orbits. If you knew where to look, this planet-sized object would be visible through a suitable telescope. And Konstanin Batygin and Michael Brown believe they do know.

As they write in the Astronomical journal, they have analyzed the orbits of Kuiper Belt objects and found six that behave in a peculiar way. As the diagram shows, the points of closest approach of these objects to the sun, known as their perihelia（近日点）, almost coincide. Moreover, these perihelia all lie near the ecliptic（黄道）---the plane of Earth’s orbit and also, approximately, that of the other planets---while the objects’ orbits are all angled at 30° below the ecliptic. The chance of all this being a coincidence, the two researchers estimate, is about seven in 100,000. If it is not a coincidence, it suggests the six objects have been guided into their orbits by the gravitational intervention of something much larger.

A computer analysis Dr Batygin and Dr Brown performed suggests this something is a planet weighing 5-15 times as much as Earth, whose perihelion is on the opposite side of the sun from the cluster, and which thus orbits mainly on the other side of the solar system from the objects its orbit has affected. This planet’s perihelion would be 200 times farther from the sun than Earth’s, and the far end of its orbit might be as much as six times that distance away. This gives a search zone, and Dr Batygin and Dr Brown are using Subaru, a Japanese telescope, to perform that search.

Given other demands on Subaru’s time, it might take five years for this search to find (or not find) the hypothetical planet. But looking at some existing data from. The Widefield Infrared Survey Explore, a satellite, might also show it, if it is there to be seen.

Ironically, it was Dr Brown as much as anyone who was responsible for Pluto’s downgrading, for he discovered Eris, an object almost as big as Pluto, in 2005.

That discovery did much to damage Pluto's planetary proof. By his own admission, he was skeptical that the anomalies he and Dr Batygin have investigated actually would point to the existence of a replacement ninth planet. He is a skeptic no longer. Whether he is actually right may soon become apparent.

1.According to Dr Batygin and Dr Brown’s research, it is quite possible that ________.

A. Pluto will restore its status as a planet of the solar system

B. the six objects in the Kuiper Belt sharing some similarities is a mere coincidence

C. there are nine planets in the solar system

D. Eris is a replacement ninth planet of the solar system

2.Which of the following is NOT true about the hypothetical planet?

A. It may have changed the orbits of six objects in the Kuiper Belt.

B. You can see it through a domestic telescope if you know where to look.

C. Compared to earth, the distance from its perihelion to the sun is about 200 times larger.

D. A satellite may be able to provide some evidence of its existence.

3.What does the underlined word anomalies stand for?

A. Six objects behaving in a peculiar way.

B. Pluto’s downgrading.

C. The discovery of Eris.

D. Some existing data.

4.The purpose of the third paragraph is to ________.

A. explain why the scientists believe there is an unfound planet

B. show how the scientists analyze the orbits of Kuiper Belt objects

C. tell us that the perihelia of the six objects almost coincide

D. introduce the two scientists’ article in the Astronomical Journal