题目内容：

Astronomers have captured(捕获) the first direct image of a planet being born.

Adam Kraus, of the University of Hawaii’s Institute for Astronomy, said the planet is being formed out of dust and gas circling a 2-million-yea-old star about 450 light years from Earth.

The planet itself, based on scientific models of how planets form, is believed to have started taking shape about 50,000 to 100,000 years ago.

Called LkCa 15b, it’s the youngest planet ever observed. The previous record holder was about five times older.

Kraus and his colleague, Michael Ireland from Macquarie University and the Australian Astronomical Observatory, used Keck telescopes on Mauna Kea(a volcano on the island of Hawaii, US) to find the planet. Kraus presented the discovery Wednesday at NASA’s Goddard Space Flight Center in Maryland.

Observing planets while they’re forming can help scientists answer questions like weather planets form early in the life of a star or later, and whether they form relatively close to stars or father away.

Planets can change orbits(轨道) after forming, so it’s difficult to answer such questions by studying older planets.

“These very basic questions of when and where are best answered when you can actually see the planet forming, as the process is happening right now,” Kraus said.

Scientists hadn’t been able to see such young planets before because the stars they’re circling around outshine(光亮强过) them. Kraus and Ireland used two techniques to overcome this problem.

One method, which is also used by other astronomers, was to change the shape of the telescope mirrors to remove light distortion(扭曲) created by the Earth’s atmosphere. The other method they used, which was unique, was to put masks with several holes over most of the telescope mirrors. The combination of these techniques allowed the astronomers to obtain high-quality images that let them see the planet next to the bright star.

The star LkCa 15—the planet is named after its star—was the team’s second target. They immediately knew they were seeing something new, so they plan to gather more data on the star.

1.The research on younger planets helps scientists _____________.

A. study why planets change orbits after forming

B. understand how planets move around their stars

C. answer questions about the age of stars and planets

D. know the relationship between planets and their stars

2.Why are young planets like LkCa 15b hard to discover?

A. Their stars are brighter than them..      B. They are very far from the earth.

C. They are generally too small.           D. They rarely form.

3.According to the text, Kraus and Ireland _____________.

A. have been working in the same university

B. observed the planet on a volcano in Hawaii

C. used two new methods in the observation

D. cut holes in the mirrors when observing

4.Which of the following would be the best title for the text?

A. Youngest planet seen as it’s forming.

B. Planet 450 light years away discovered.

C. World’s first direct image of a planet taken.

D. New technique helps discover young planets.