第一节 完形填空（共15小题; 每小题2分，满分30分）阅读下面短文，掌握其大意。然后从1～15各题所给的四个选项（a、b、c和d）中，选出最佳选项，并在答题卷上将该项涂黑。 march 21st is world sleep day. this year’s slogan is “breathe easily, sleep well”. it 1 to celebrate the benefits of good and healthy sleep. sleep is like food for the 2 . enough sleep helps the body and brain grow and 3 . according to the national sleep foundation in the us, 4 need seven to nine hours of sleep every night. for students aged 10 to 17, a 5 amount is about eight to nine hours per night. but many students don’t get 6 sleep because of early school start times and heavy 7 . about 80 percent
