阅读下面短文，从短文后所给各题的四个选项(A、B、C和D)中选出能填入相应空白处的最佳选项。

In the jungle (丛林) you may get hopelessly lost within five minutes after starting. That is (36) you should always carry a compass (指南针). In open country, during the day, you can (37) which way to go by studying the (38) . At night, the stars are sure (39) to direction. In most places the jungle rooftop (顶) is so (40) that it is (41) to see the sun or the stars. (42) you must check your position by the (43) . Keep watchful (注意的，警惕的). Watch the ground in front of you carefully. (44) and listen now and a gain. Avoid (45) , and rest often. In a place (46) is hot and damp, the person who walks fast will soon become (47) . A steady (稳定的), slow step is wisest in the long run. If you (48) your way, don’t be scared (恐惧的). Try to (49) how long it has been (50) you were sure of your position. Make a mark (51) you are on a tree. Put the marks on (52) of the trees, so that you’ll be a ble to see them from any (53) . Then you can begin retracing your steps (顺原路返回) , knowing that you can always find the place (54) which you started. (55) try to travel through the jungle at night except in an emergency (紧急情况).