短信预约提醒成功
1、Greek soldiers sent messages by turning their shields（盾）toward the sun. The flashes reflected light could be seen several miles away. The enemy did not know what the flashes meant, but other Greek soldiers could understand the messages.
Roman soldiers in some places built long rows of signal towers. When they had a message to send, the soldiers shouted it from tower to tower. If there were enough towers and enough soldiers with loud voices, important news could be sent quickly over distance.
In Africa, people learned to send messages by beating on a series of large drums（鼓）. Each drum was kept within hearing distance of the next one. The drum beats were sent out in a special way that all the drummers understood. Though the messages were simple, they could be sent at great speed for hundreds of miles.
In the eighteenth century, a French engineer found a new way to send short messages. In this way, a person held a flag in each hand and the arms were moved to various positions representing different letters of the alphabet. It was like spelling out words with flags and arms.
Over a long period of time, people sent messages by all these different ways. However, not until the telephone was invented in America in the nineteenth century could people send speech sounds over a great distance in just a few seconds.
65. According to this passage, the Roman way of communication depended very much upon .
［A］ fine weather
［B］ high tower
［C］ the spelling system
［D］ arm movements
66. Which of the following statements is true?
［A］ Neither the Greek soldiers nor their enemy could understand the message.
［B］ African soldiers shouted from tower to tower to pass message.
［C］ Telephone was invented by a French engineer.
［D］ Only by using telephone could people send speech sounds quickly.
67. The African way of communication sent messages.
［A］ in a special way
［B］ over a very short distance
［C］ by a musical instrument
［D］ at a rather slow speed
68. The way of communication made use of visible signs.
［A］ French
［B］ Roman
［C］ African
［D］ American
2、Because we can feel that things are heavy, we think of weight as being a fixed quality in an object, but it is not really fixed at all. If you could take a one pound packet of butter 4, 000 miles out from the earth, it would weigh only a quarter of a pound.
Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4 000 miles out into space? The reson is this: All objects have a natural attraction for all other objects; this is called gravitational attraction, but this power of attraction between two objects gets weaker as they get farther apart. When the butter was at the surface of the earth, it was 4 000 miles from the centre （in other words the radius（半径）of the earth is 4 000 miles）. When we took the butter 4 000 miles out, it was 8 000 miles from the centre, which is twice the distance.
If you double the distance between two objects, their gravitational attraction decreases（减少）two times two. If you treble（翻三倍）the distance, it gets nine times weaker（three times three）. If you take it four times as far away, it gets sixteen times weaker（four times four）and so on.
69. The best title for this passage is.
［A］ The Earth Weight
［B］ Weight in Space
［C］ Changing Weight on the Earth
［D］ Weight on and off the Earth 转贴于：考试大_PETS考试
70. We can feel things are heavy because.
［A］ weight is a fixed quality in an object
［B］ they are far away from the centre of the earth
［C］ of the earth's strong attraction for them
［D］ they are not taken away from the surface of the earth
71. If the distance between two objects is shortened by half, their gravitational attraction will.
［A］ double
［B］ become four times stronger
［C］ be the same
［D］ get four times weaker
72. If an object weighed one pound 8 000 miles above the earth, it would weighon the surface of the earth.
［A］ 6 pounds
［B］ 4 pounds
［C］ 9 pounds
［D］ 1/9 pound
65?从第二段可以推知答案为D。
66?该题可以通过排除而得知答案为D。
67?鼓为一种乐器，所以本题答案为C。
68?法国工程师发明的用旗语表示拼写字母的方式是可以看到的，本题答案为A。
69?本篇短文介绍的是物体在空中和在地球上重量不同的原因，因此恰当的标题应是D。
70?我们之所以能感觉到重量是因为地球引力的原因，答案为C。
71?72?为计算题，71答案为B，72为C。
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