完形填空。 IntheUSA，childrenstartschoolwhentheyarefiveyear...
问题详情：完形填空。 IntheUSA，childrenstartschoolwhentheyarefiveyearsold．Insomestatestheymuststayinschool 1 theyaresixteen．Butmoststudentsareseventeenoreighteenyearsoldwhenthey 2 ，secondaryschools．T...