第二节 完型填空
阅读下面短文，从短文后所给各题的四个选项(A、B、C和D)中选出能填入相应空白处的最佳选项。
"Sesame Street" has been called "the longest street" in the world. That is 【B1】 the television program by that name 【B2】 now be seen in so many parts of the 【B3】 . That program became one of 【B4】 exports soon after it went on the 【B5】 in New York in 1969.
In the United States more than six million children watch the program 【B6】 . The viewers include more than half the nation’s pre-school children, 【B7】 every kind of economic racial (种族的) and geographical 【B8】 .
"Sesame Street" uses songs, stories, jokes and pictures to give children a basic 【B9】 of numbers, works and human relationships. Although some educators object to certain elements in the program, parents 【B10】 it highly. Many teachers also consider it a great help, though some teachers 【B11】 that problems arise when first graders who have heard from "Sesame Street" are in the same class with children who have not watched the program.
Why has "Sesame Street" been so much more 【B12】 than other children’s shows？ Many reasons have been suggested. People mention the 【B13】 theories of its creators (创造者), the support by both government and private business, and the 【B14】 use of a variety of TV tricks. 【B15】 an equally important reason is that mothers watch "Sesame Street" 【B16】 their children. This is partly because 【B17】 adult stars often appear on "Sesame Street". But the 【B18】 reason for the program may be that it 【B19】 every child watching it feel able to learn. The child finds himself 【B20】 , and he wants to learn more.
【B1】

A. why
B. how
C. because
D. as if