Astronomers (天文学家) say they are on the point of finding planets like Earth orbiting other

Astronomers (天文学家) say they are on the point of finding planets like Earth orbiting other stars, which is a key step in determining if we are alone in the universe.
A top NASA official and other leading scientists say that within four or five years they should discover the first Earth-like planet where life could develop, or may have already. A planet close to the size of Earth could even be found sometime this year.
At the annual American Astronomical Society conference this week, each discovery involving  so-called “exoplanets” —those outside our solar system —pointed to the same conclusion：Quiet planets like Earth where life could develop probably are plentiful.
NASA’s Dew Kepler telescope and a lot of new research from the suddenly hot and petitive exoplanet field caused noticeable buzz at the meeting．Scientists are talking about being at “an incredible special place in history” and closer to answering the question. “Are we alone? For the first time, there’s an optimism that sometime in our lifetimes we’re going to get to the bottom of that,” said Simon Worden，an astronomer who heads NASA’s Ames Research Center. “If I were a betting man, which I am, I would bet we’re not alone.”
“These are big questions that reflect upon the meaning of the human race in the universe,” the director of the Vatican Observatory, the Rev. Jose Funes, said Wednesday in an interview at this week’s conference.
Worden told The Associated Press: “I would certainly expect in the next four or five years we’d have an Earth-sized planet in the habitable (可居住的) zone.”
What is very important in determining if we are alone in the universe?
A. Finding an Earth-like planet.       B. Orbiting other stars.
C. Developing new telescopes.      D. Finding more exoplanets.
What’s an exoplanet?
A. It’s a planet like Earth.        B. It’s a planet outside our solar system.
C. It’s a planet orbiting the sun.   D. It’s a planet where life have developed.
The underlined phrase “get to the bottom of” probably means “    ”.
A. understand fully    B. make full use of
C. search for         D. do more research on   
From the passage we can learn that     .
A. an Earth-like planet has been found
B. it’s been proved we are not alone in the universe
C. Jose Funes has found the meaning of the human race in the universe
D. the discovery of an Earth-like planet could happen in the near futureA