题目

When a big boat, like a cruise ship, goes through the ocean, it often creates waves. This happens when the large engines on the back of the cruise ship cause the water on the ocean’s surface move up and down violently. These waves move out from the boat in both directions. If you are captaining a smaller boat, you’d better steer clear of a ship’s wake, so that your boat is not surfing on the waves, causing it to overturn. A wave is a pattern of motion. When you look at a wave, it may appear as simply water moving across the surface of the ocean. In fact, this is false. The water is actually not moving in the same direction as the wave. While the wave itself -- the pattern of motion – is moving across the surface of the ocean, the water is actually moving in a circular motion, which brings the water molecules back to their original position. The water merely gives the appearance of moving forward. If this is confusing, think of the kind of wave you do at a baseball stadium. Viewed from a distance, the wave is clearly moving across the stadium. But the thing that makes up the wave – the people – are not moving across the stadium, they’re just moving up and down in their seats. This is just like the water in an ocean wave. A lot of water is moving up and down, which gives water the appearance of moving along with the wave. Surfers pay a lot of attention to waves. If you’re not in an area where the waves are suitable for surfing, then you can’t surf. Usually, surfers gather in areas known for big waves – waves that rise high off the ocean’s surface. If the wave is bigger, then the surfer is often able to surf for longer distances and perform more tricks. The height of a wave is known as its amplitude ( 振幅,幅度,波幅) . If you could make a wave freeze, then you could measure the wave’s amplitude by running a tape measure from the ocean’s surface to the very peak of the wave. All waves can be measured using amplitude and wavelength. While the waves created by a boat have very small amplitude – sometimes as small as a few centimeters – the wavelength can be very short, as lots of waves are being generated. By contrast, a tsunami has very high amplitude, sometimes more than 100 feet, but a relatively long wavelength, as it’s a high wave. Waves generated in the same way can have great differences in amplitude and wavelength. For example, think back to the cruise ship. While each ship creates waves caused by the movement of the boat, the properties of each of the waves may be very different. For example, a larger cruise ship, with powerful engines, may create a wave that has high amplitude and a short wavelength. However, if the ship’s engines slow down, they may then start creating less powerful waves at a slower rate. This would cause the waves’ amplitude to decrease, but its wavelength to increase. 63. What does the phrase “steer clear of a cruise ship’s wake” in the 1st paragraph mean? A. keep awake while steering a ship         B. get a clear view of what is ahead C. keep away from the cruise ship                   D. follow the cruise ship very closely 64. The author gives an example of wave people do in the stadium in order to _____________. A. describe how excited people are in a basketball stadium B. clear the confusion over measuring the wave’s amplitude C. demonstrate how to make waves in a basketball stadium D. explain why the water appears to move along the waves 65. The last paragraph gives us the impression that ________________. A. the wave’s amplitude may vary, but its wavelength remain the same B. the more powerful the ships engines are, the higher the waves they generate C. the amplitude of a wave depends on the direction the water moves forward D. measuring the amplitude and wavelength of waves is not quite easy 66. What is this passage mainly about? A. How waves are created and measured. B. What makes the sea water move forwards. C. Why people create waves in the stadium. D. How to steer a cruise ship in the rough sea. 答案：CDBA

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