It's commonly believed that school kids started taking summers off in the 19th century so they'd have time to work on the farm. Nice as that story is, it isn't __1__. Summer vacation has little to do with working in the __2__ and more to do with __3__， rich city kids playing hooky (逃学) and their parents.

　　Before the Civil War, farm kids __4__ had summers off. They went to school during the hottest and __5__ months and stayed home during the spring and fall, when crops needed to be planted and __6__. Meanwhile, city kids hit the books all year long - __7__ included.

　　But as cities got more crowded, they got hotter, __8__ the "urban heat island effect". That's when America's middle and upper class families started __9__ cities and went to the cooler __10__. And that caused a problem. School __11__ wasn't compulsory back then, and __12__ were being left half­empty each summer.

　　Lawmakers started arguing that kids should get summers off anyway. It helped that, culturally, __13__ time was becoming more important. With the dawn of labor unions and the eight­hour workday, working adults were getting more time to themselves. Advocates for vacation time also __14__ (incorrectly) that the brain was a muscle, and like any muscle, it could suffer injuries if __15__. From there, they believed that students shouldn't go to school year­round. What is more, air conditioning was decades away, and city schools during summertime were like __16__.

　　So by the turn of the century, urban districts had managed to cut about 60 schooldays from the hottest part of the year. Rural schools soon __17__ the same pattern __18__ they wouldn't fall behind. Business folks obviously saw a(n) __19__ here. The summer vacation business __20__ ballooned into what is now one of the country's largest billion­dollar industries.

　　1．A.true B．funny

　　C．bad D．fair

　　2．A.factories B．schools

　　C．fields D．teams

　　3．A.smart B．sweaty

　　C．strong D．sweet

　　4．A.always B．never

　　C．still D．also

　　5．A.coldest B．longest

　　C．best D．busiest

　　6．A.watered B．covered

C．harvested D．cleared