三、任务型阅读
Every school day, we use schoolbags to carry all of our things to school. They are a big part of our lives. But have you ever thought about the history of the schoolbag?
In the Han Dynasty, students in old-style private schools used bamboo boxes to carry books to school. People consider the bamboo boxes to be the earliest schoolbags. There were usually two or three layers（层）in the box. Kids put different things like books, brushes and paper in the boxes.
Hundreds of years later, people developed a new kind of schoolbag called the budai because it was lighter than the bamboo box. With the founding（成立）of the People's Republic of China, military rucksacks（军用帆布包）became popular. Many people carried them when they were in school. Ask your grandparents or parents about these bags. Maybe they can tell you about their experiences of carrying them when they were in school.
More styles of schoolbags have appeared in recent years. Many of them have colourful and fashionable designs on them, such as pictures of cartoons or pop stars. And they are more comfortable to use. Some students pull wheeled bags filled with heavy textbooks and others carry backpacks.
Schoolbags are still changing. Can you imagine what future schoolbags will be like?
14. What are considered to be the earliest schoolbags?（不超过5个词）
______
15. Why did people develop the budai as the school bag hundreds of years ago?（不超过10个词）
______
16. When did the military rucksacks become popular?（不超过10个词）
______

The bamboo boxes. ; Because it was lighter than the bamboo box. ; With the founding of the People's Republic of China.