题目

. 第二部分：阅读理解（共两节，满分50分） 第一节（共20小题，每小题2分，满分40分）阅读下列短文，从每题所给的四个选项A、B、C、D中选出最佳选项。 Judging from recent surveys, most experts in sleep behaviour agree that there is virtually an epidemic （流行病）of sleepiness in the nation. “I can’t think of a single study that hasn’t found Americans getting less sleep than they ought to,” says Dr. David. Even people who think they are sleeping enough would probably be better off with more rest. The beginning of our sleep-defi一个等腰三角形的边长分别是4cm和9cm，则它的周长是________cm