The world is not coming to an end on December 21st, 2012, the US space agency announced to dispel （消除） widespread rumors fueled by the Internet and a new Hollywood movie．
The latest big screen 2012 was based on stories according to the Mayan calendar．It showed that by the end of 2012, a Planet X will collide （碰撞） with the earth．
Some websites accuse NASA of hiding the truth on the planet's existence, but the US space agency considered such stories as tricks．"There is no basis in fact for these claims," NASA said in its website．"If such a collision were real, scientists would have been tracking it for at least the last decade, and we would see itwith our eyes now．Obviously, it doesn't exist and there will be no threat to the earth in 2012," it insisted．"After all, our planet has been getting along just well for more than four billion years," added NASA．
There is another planet, Eris, floating in space．But the small planet will remain safely fixed in the outer solar system and it can come no closer than four billion miles to the earth, according to NASA．
And even if the planets were to line up as some have forecast, the effect on our plant would be very little．"And while comets and asteroids （小行星） have always hit the earth, big hits are very rare," NASA noted．The last major collision was believed to be 65 million years ago, resulting the end of dinosaurs （恐龙）．
"We are sure that there are no threatening asteroids as large as the one that killed the dinosaurs," the space agency said．
．What played a key role in the spread of the rumors?

A．The Internet and the film 2012．

B．The Mayan calendar．

C．The US space agency．

D．The television screen．

．The underlined word "it" in Paragraph Three probably refers to _    ___．

A．the collision	B．the Planet X
C．the threat	D．the NASA website

．We can conclude from the passage that __   __．

A．the film 2012 is well accepted in the science field

B．scientists have been tracking Planet X for over ten years

C．the earth will exist for more than four billion years

D．the rumors caused a panic among some people

．What do we know about Eris according to the passage?

A．It doesn't exist in the universe．

B．It won't threaten the earth．

C．It is too far to be seen．

D．It is similar to the earth.