四、综合填空(共20空,每空1.5分,计30分)
阅读下面的短文,根据短文内容,从下面万框内所给11个词中选择10个意义相符的词,必要时进行词形变化,填入空白处,每空一词。
（it, stone, six, by, easy, how, bulding. good, against, however, although）
The Juyongguan Great Wall was built during the Spring and Autumn Period. It was rebuilt and repaired for the (51)____time in the early Ming Dynasty, which makes it look like what it is today. Recently, a group of scientists from China Agricultural University in Beijing made a study on the Juyongguan Great Wall, and they found an amaning fact.
Some parts of the wall were made of (52)___,but some were built of "rammed earth", which is a mixture of rocks and soil. Usually, rammed earth should be destroyed(破坏)(53)___by wind and rain over time.(54)____, the fact is not like that. So scientists questioned (55)_____rammed earth managed to survive for such a long time. And now they have found that parts of the wall have been protected(56)____something called biocrust(生物结皮).This is a thin layer of plant life. including moss(苔藓)，lichen(地衣)and other things.
The scectists examined a 370-mile-long section of the wall and found that the parts covered in biocrust remained (57)____than other parts. The scientists took some samples(样本)of the biocrust back to their lab for testing. They found the natural material was actually much stronger (58)____the rain and wind than the rammed earth. This means that the wall has protected (59)____well with the bnocrust over the years.
These findings could be important. (60)_____biocrust may not look attractive, its natural ability to protect things could be a very useful tool. It offers the experts who manage ancent buildings a good way to protect them.
答案解析：
51. sixth。表示“第六次”，用序数词。
52. stone。根据后文“but some were built of "rammed earth"”可知这里说墙的材料，stone“石头”符合。
53. easily。这里需要用副词修饰动词“be destroyed”，easily表示“容易地”。
54. However。表示转折，与前文形成对比。
55. how。根据“questioned”可知科学家想知道夯土是如何长时间留存的，用how。
56. by。“be protected by...”表示“被……保护”。
57. better。根据“than”可知要用比较级，这里表示有生物结皮覆盖的部分比其他部分保存得更好。
58. against。“against”有“抵御”之意，这里表示抵御风雨。
59. itself。这里指长城自身，用反身代词。
60. Although。引导让步状语从句，表示“虽然”。
