42. get confused感到困惑 43. take turns轮流

44. be prepared to准备... 45. no matter how无论怎样

46. refer to 指的是...参考...查阅... 47. be rich in富含...

48. be good for对...有好处 49. reduce diseases减少疾病

50. the water supply水的供应 51. year after year一年又一年

52. as a result结果 53. get exhuasted感到筋疲力尽

54. insist on坚持 55. every two or three years每两三年

56. write a summary of...写...的总结 57. exchange...with...与...交换...

58. give each other comments互相评论 59. be free of远离...

60. that is to say那就是说