阅读理解。 What looks like a black hole, behaves like a black hole, but is bigger than a black hole? Two black holes! Astronomers last week discovered a pair of enormous black holes far out in the galaxy that appear to be dancing toward each other. However, astronomers say the collision is not likely to occur for several million years. Black holes are objects in outer space that are so dense that nothing can escape their gravity. They often sit in the center of a galaxy - like the Milky Way - and suck up everything near them. The gravitational pull of a black hole is so intense that not even light (Which travels faster than anything else in space) can make it past without being swallowed. Black holes, like the one at the center of the Milky Way, are enormous. Scientists call some of them 'supermassive', because they can be a few million times the size of most stars. Their size, their mass, and their inescapable gravity make black holes a giant force of nature in outer space. Because there is no light near black holes, astronomers cannot actually see them; they are completely invisible to us on the Earth. Scientists manage to detect the existence of a black hole by watching what happens to other objects, or matter floating in space. So how did scientists manage to get a good look at a region so faraway? The team used an orbiting NASA observatory known as Chandra. This special observatory uses X-rays rather than light to watch far out into space. Right before a star gets sucked into a black hole, it produces a large number of X-rays. 1. Which of the following statements CANNOT be used to describe a black hole? A. It is an object in space that can be seen on the Earth. B. It has extremely strong gravity. C. It can suck up everything near them. D. It is an enormous object in the galaxy. 2. Why did the astronomers need to use Chandra? A. Because Chandra can throw light on black holes. B. Because Chandra can help them see black holes in X-rays. C. Because Chandra was sucked into the black hole. D. Because Chandra can resist the gravitational pull of a black hole. 3. Which of the following is NOT discussed in the passage? A. Why black holes get an immense force of nature. B. How stars react when sucked into a black hole. C. Black holes' swallowing up many nearby stars. D. How black holes come into existence. 4. Which is the latest space discovery about black holes? A. Two black holes appear to be advancing toward each other. B. The location of black holes in the galaxy. C. New clues about the beginning of the universe. D. Nothing near a black hole can escape without being swallowed.