阅读理解。
The moon is the earth's largest and only natural satellite. A satellite is a small body that goes around a
planet. The first man-made satellite went into the orbit in 1957. By 1968 there were over three hundred
satellites in the orbit. Some satellites send back weather pictures. Others send out radio waves. Some
satellites are what we call "junk". In 1963, the United States put millions of small pieces of wire into orbit.
They were used to carry radio waves. Many of these wires may still be there. Some space junk was not
put in the orbit. For example, one piece of space junk is a glove lost by an astronaut!
Space is very big. Does it matter if there is junk in the orbit? Many scientists think so. They say we
must pay much attention to how we use this new resource. They think anything man puts into space
should be made to come back to earth when its work is done. They say it's dangerous to have space junk,
because it's possible for spacecraft to collide with the junk.
1. The first man-made satellite was sent up into space in _____.
[ ]
A．1957
B．1963
C．1968
D．1975
2. There were
satellites in orbit by 1968．
[ ]
A．less than 300
B．about 30
C．more than300
D．about300
3. The underlined word "junk" in the first paragraph means _____.
[ ]
A．飞行物
B．陨星
C．天体
D．垃圾
4. Lots of scientists think that all the space junk should be
.
[ ]
A．kept in space
B．used to do something for humans
C．made to come back to earth
D．put together