读《鸟鸣涧》，桂花花朵极小，“桂花落”声音极细微，诗人如何能感受到？

在做观察蚯蚓的实验时，同学们发现蚯蚓的体表是有黏液的，这些黏液有利于蚯蚓（    ）

任务型阅读
    Chinese writer Mo Yan won the 2012 Nobel Prize in Literature(诺贝尔文学奖)．He is the first Chinese to win the prize．
    Mo Yan was born into a farmer's family in Shandong in 1955．He left school to work at the age of twelve，first on the farm，later in a factory．In 1 976 he joined the PLA and during this time he began to study writing．His first short story was published(出版)in 1981．He has written many famous books about his childhood and his home town．Many of his books were translated into English，French and many other languages．
    Mo Yan's winning of the Nobel Prize in Literature，widely regarded as(被认为)a great encouragement for China's literature，is bringing more confidence to the nation's young authors．
根据短文内容，回答下列问题。

“北通涿郡之渔商，南运江都之转输，其为利也博哉!”这是古人对大运河这一历史工程的赞颂。

复数的共轭复数是           （   ）