{an}为等差数列，公差为d，Sn为其前n项和，S6＞S7＞S5，则下列结论中不正确的是（ ）
A．d＜0
B．S11＞0
C．S12＜0
D．S13＜0
由已知条件
s6＞s7⇒s6＞s6+a7⇒a7＜0 s7＞s5⇒s5+a6+a7＞s5⇒a6+a7＞0 s6＞s5⇒s5+a6＞s5⇒a6＞0
即a6＞0，a7＜0，a6+a7＞0，
因此d＜0，A正确；
S11=11a6＞0，B正确；
S12=
=12(a1+a12) 2
＞0，故C错误；12(a6+a7) 2
S13=
=13a7＜0，故D正确，13(a1+a13) 2
故选C．
| Children’s literature traces its beginnings to preliterate times, when ancient storytellers passed tales and legends from generation to generation in the oral tradition. William Caxton, who established England’s first printing press, published books of etiquette, fables and legends. However, these didn’t constitute a body of work that could be considered literature for children. Because children at that time were considered "miniature adults", books were didactic in nature. The content for young readers consisted mainly of religious instruction, rules of behavior, ethical messages, and moral platitudes. In 1774, Englishman John Newberry changed children’s publishing when he began to create books with attractive formats, quality illustrations, and sturdy bindings, that were designed primarily for children to enjoy. The oldest, and most prestigious award given for children’s books published in America, is the Newberry Medal. In the following century, children’s literature began to bloom. Hans Christian Andersen’s wonderful stories like "The Ugly Duckling", and "The Little Mermaid", and Grimm brothers collected two volumes of German folktales that included stories such as "Snow White" and "Rumpelstiltskin". Childhood came to be recognized as a joyful and carefree period of life, and books celebrating it began to be published. Charles Dodgson (Lewis Carrol) wrote the fantasy "Alice in Wonderland", the first book that was intended purely for children’s enjoyment without any pretense of instruction. Edwards Lear’s books of nonsense poetry delighted both young and old readers. In North America, books for a young audience were becoming popular as well. Kate Douglas Wiggin wrote "Rebecca of Sunnybrook Farm", Louisa May Alcott wrote "Little Women", and Samuel Clemens (Mark Twain) created Tom Sawyer and Huckleberry Finn. By the end of the century, the pious and moralistic books of earlier times had been replaced by writing designed to amuse and entertain a young audience. In the 1800s color printing was introduced, and by the middle of the 19th century, the rough illustrations that characterized earlier children’s books had been replaced by works of art that captured the word and some of the story. |
According to the passage, "Alice in Wonderland" was an example of ______.
A．a fantasy story
B．a German folktale
C．a book celebrating childhood
D．a book of instruction