答案
1-10：ACBBA CBCBC 11-18：DA/BCD/BCC 19—23：CEAGF
24—43: BAADB/ CCDAC/BDABD/ABCCB
44. are protected 45. rapidly 46. strangers 47. cleaned 48. your 49. Having 50. or 51. that/which 52. off 53. when /while 参考范文
With global warming and melting ice, some scientists think that polar bears could die out by the end of the century. However, other scientists think that polar bears could die out by the end of the century. However, other scientists don’t think so. They have found polar bars have found alternative food sources and they can survive by hunting animals on land instead of your seals. The researchers expect all polar bears learn how to hunt on land to avoid starvation.