【正确答案】 B

【答案解析】[听力原文] Good morning, today's lecture is about an interesting topic, that is, travelling in the jungle. Jungle is a fantastic place for people who like adventure and exploration. But never forget the danger in the nature. As we all know, jungle country is not friendly to man, but it is possible to survive there. You must have the right equipment and you must know a few important things about woodcraft. No one should go into the jungle without the right equipment. You need lightweight clothing, a good knife, and a compass. Fishhooks and a line, a rifle and ammunition, matches in a waterproof container are necessary too. So is a mosquito net. In the jungle you can get hopelessly lost within five minutes after leaving a known landmark. That is why you should always carry a compass. In open country, during the day, you can tell which way to go by studying the sun. At night the stars are sure guides to direction. But in most places the jungle rooftop is so thick that it is impossible to see the sun or the stars. Keep alert. Watch the ground in front of you carefully. Stop and listen now arid again. Avoid haste, and rest often. You will soon become exhausted if you set a fast pace in a hot and humid place. A steady and even pace is wisest in the long run. Keep calm if you lose your way. Try to decide how long it has been since you were sure of your position. Cut marks on four sides of a tree, so that you will be able to see them from any direction. Except in an emergency, never try to travel through the jungle at night. Whenever possible, it is wise to follow streams and rivers that run in your general direction. This may give you many extra miles of travel. But in the end it will save time and energy. Nothing is more exhausting than hacking a trail cross-country through unbroken jungle. Bamboo grows along the banks of many jungle streams. Since it is hollow and extremely strong, it makes a perfect raft. Mosquitoes and some other insects will be with you the entire time .The only defense against them is to wear the fight kind of clothing. You should never wear shorts in the jungle. Your trousers must be lightweight and long. The cuffs should be tucked into your boot tops. Finding water that is safe to drink can be a problem. Many clear and fresh-looking streams and rivers carry deadly germs. Such water must always be boiled before you drink it. Luckily, the jungle has many kinds of plants and vines that give water. Water from almost all plants is pure enough to drink. But stay away from vines that have bitter or milky sap. Many jungle plants also provide food. Before you go into the jungle, learn to recognize the varieties of plants that can be eaten. If you haven't had a chance to do this, watch what kinds of fruit and nut the birds and monkeys choose. Such food is almost always safe for man. When you see an animal in the jungle, you can be sure that the source of food is somewhere close by. That source may mean for you a difference between going to sleep well-fed or hungry. Surviving in the jungle is a science. The jungle people have become perfect in this science, and you can too. Learn as much as you can about what to expect in the jungle. Make sure you have the right equipment. Then no part of the jungle will seem unfriendly or frightening. In fact, you will be able to 'live off' it for a long time. Thank you for your attention. I believe this lecture could offer some help to friends who are obsessed in travelling. In the jungle, why should you always carry a compass? 细节题。讲座中提到，在丛林里，如果你离开一个你所知道的路标，五分钟内你就会绝望地发现你迷路了，因此你应当携带一个指南针。由此可知，携带指南针是为了防止迷路：In the jungle you can get hopelessly lost within five minutes after leaving a known landmark. That is why you should always carry a compass. 因此，答案为B。