如图是一个池塘生态系统，请分析回答下列问题：

（1）在此生态系统中，生产者是____ ；在该生态系统中，没有画出的生物有____ ，它们在生态系统中也是具有重要作用的．

（2）如向池塘中投放一些大黑鱼 （肉食性），则池塘中小鱼的数量将会____ ，写出这条食物链____ ．

（3）一段时间后，该池塘中各种生物数量又会处于____ 状态．说明生态系统具有一定的____ 能力．

（4）如果该生态系统受到有毒物质的污染，那么体内积存有毒物质最多的生物会是____ ．

（5）为维持这一水域生态系统的平衡，作为中学生的你，能够做些什么？____ ．

已知⊙O半径为2,弦BC的长为$2\sqrt{3}$,点A为弦BC所对劣弧上任意一点. 则∠BAC的度数为____． 

    Children all round the world are familiar with fairy tales such as “The Little Mermaid”(美人鱼), “The Princess and the Pea” and “The Emperor's New Clothes”. The colourful 1 from the stories made us laugh and cry throughout our 2.

    The stories are the creation(创作) of Danish writer Hans Christian Anderson. He was born into a 3 family in Odense, Denmark, on April 2, 1805. His 4 life was not easy. His father was a shoemaker and his mother a washerwoman. He 5 very little education. As a child he was very6 and was laughed at for being feminine (女性化的) and tall.

    In 1816 his father died and Anderson was 7 to go out to work, first in a tailor's shop and 8 at a tobacco factory. 9 the age of 14 Anderson moved to Copenhagen to start a career as a singer and actor. He struggled for three years 10 he had to leave the theatre when his voice 11 in 1822.

    12, Anderson went to a grammar school. Having done well, he was admitted to Copenhagen University in 1828. He began to publish his fairy tales in 1835. They 13 in small volumes (量) until his death.

    14 Anderson lived a 15 life, he tried to make people 16 in all his stories. He wrote because he didn't want children to have a 17 childhood as he did. The works 18 Anderson world fame(声誉), but he remained a 19 man. He never married and his friends were the people who paid for his work. Anderson 20 on August 4, 1875. His home in Odense is now a museum and thousands of people visit it every year.