46. A. atmosphere B. experience C. experiment D. sight
47. A. seen B. observed C. explored D. studied
48. A. scientists B. climbers C. locals D. officials
49. A. holding on to B. going back to C. setting out to D. giving way to
50. A. changes B. clears C. improves D. permits
51. A. Obviously B. Easily C. Absolutely D. Finally
52. A. keeping B. ruining C.replacing D. creating
答案38-42 DCBAC 43-47 ACDBA 48-52 BDADB