For over 350 years men have used telescopes to find out more about the stars and planets. Our knowledge of the stars has increased very greatly since Galileo, the famous Italian scientist, made the first telescope in 1609. Men have used telescopes to study the moon’s surface—its craters (环形山), mountains and plains. Now men have recently built bigger and more powerful telescopes. They have discovered new groups of stars. Modem telescopes have shown us that certain stars are not single at all; they are groups of millions of stars. The largest telescope in the world has a mirror which is 200 inches wide. It is at Mount Palomar in America and it has shown us millions of new stars. The light from these stars has taken a million years tO reach the earth. The largest telescope in the world ______.
A．has recently been built in America B．is 200 in ches long C．has shown millions of new stars to us D．is the most powerful one at Mount Palomar in the U.S.