阅读理解。 You may think that sailing is a difficult sport, but it is really not hard to learn it. You do not need to be strong. But you need to be quick. And you need to understand a few basic rules about the wind. First, you must ask yourself, 'Where is the wind coming from? Is it coming from ahead or behind or from the side?' You must think about this all the time on the boat. The wind direction tells you what to do with the sail. Let's start with the wind blowing from the behind. This means the wind and the boat are going in the same direction. Then you must always keep the sail outside the boat. It should be at a 90° angle (角度) to the boat. Then it will catch the wind best. If the wind is blowing from the side, it is blowing across the boat. In this case, you must keep the sail half way outside the boat. It should be at a 45 ° angle to the boat. It needs to be out far enough to catch the wind, but it shouldn't flap (摆动). It shouldn't look like on a flagpole. If it is flapping, it is probably out too far, and the boat will slow down. Sailing into the wind is not possible. If you try, the sail will flap and the boat will stop. You may want to go in that direction. It is possible, but you can't go in a straight line. You must go first in one direction and then in another. This is called tacking. When you are tacking, you must always keep the sail inside the boat. 1. What should you consider first while sailing? A. Sailors' strength. B. Wave levels. C. Wind directions. D. Size of sails. 2. What does the word 'It' underlined in Paragraph 4 refer to? A. The boat. B. The wind. C. The sail. D. The angle. 3. What do you have to do when sailing against the wind? A. Move in a straight line. B. Allow the sail to flap. C. Lower the sail. D. Tack the boat. 4. Where can you probably find the text? A. In a popular magazine. B. In a tourist guidebook. C. In a physics textbook. D. In an official report.