Around the world more and more people are taking part in dangerous sports and activities. Of course, there have always been people who have looked for adventure(冒险)---those who have climbed the highest mountains, traveled into unknown parts of the world or sailed in small boats across the greatest oceans. Now, however, there are people who look for an immediate excitement from a risky(冒险的) activity which may only last a few minutes or even seconds. I would consider bungee(蹦极) jumping to be a good example of such an activity. You jump from a high place(perhaps a bridge or a hot-air balloon) 200 meters above the ground with an elastic(有弹性的) rope tied to your ankles. You fall at up to 150 kilometers an hour until the rope stops you from hitting the ground. It is said that about 2 million people around world have now tried bungee jumping. Other activities which most people would say are as risky as bungee jumping include jumping from tall buildings and diving into the sea from the top of high cliff(悬崖).
For the reasons, some psychologists explain that many people think their life in modern societies has become safe and boring. Not very long ago, people’s lives were constantly(持续的) in danger. They had to go out and hunt for food, diseases could not easily be cured, and life was a continuous battle (战争)for survival.
Nowadays, according to many people, life offers little excitement. They live and work in comparatively safe conditions; they buy food in shops; and there are doctors and hospitals to look after them if they become ill. The answer for some of these people is to look for danger in activities such as bungee jumping.
【小题1】Are there many people who are taking part in the dangerous sports?
【小题2】How many kinds of dangerous sports does the writer refer to?
【小题3】How long does a bungee jumping usually last?
【小题4】What do many people think of their life nowadays?
【小题5】What does the writer tell us in the last two paragraphs?

Wind is the great maker of waves. There are exceptions (例外), such as the tidal (潮汐的) waves sometimes caused by earthquakes under the sea. But the waves most of us know are caused by winds blowing over the sea .

Now let’s learn some physical (自然地理学的) things about it. A wave has height, from low point to high point . It has length (长度)--the distance from this high point to that of the following wave. The period of the wave means the time it takes for succeeding high points to pass a fixed point. None of these things stays the same--for all depend upon (依靠)the wind, upon the depth (深度) of the water and many other matters.

The water that makes up a wave does not advance with it across the sea. Each drop of water turns around in a little circle with the passing of the wave, but returns very nearly to its original position (原先的位置). And it is lucky that this is so. For if the huge groups of water that make up a wave really moved across the sea, sailing would be impossible. If we want to find the speed of a wave, we may use the following way : Speed =" wavelength" × frequency (频率).

Here, wavelength is the distance between two high points , frequency means the number of cycles per second

1.What causes waves?

2.Which of the following is TRUE according to the passage?

3.The speed of Wave 1 is 100 cm/s, frequency 10. The frequency of Wave 2 is 300, while its speed is twice that of Wave 1. Which of the following is right?

4.Where can we find this passage?