题目内容：

What time is it？There are many ways you can find out the time.You may have a watch on your wrist(手腕)．You can look at a clock on the wall.You can listen to the radio，watch TV or ring a number on the telephone to get the time.But do you know the history of how people tell the time?

It has not always been easy to know the time.A long time ago people looked at the sun to tell the time.They could tell the time of the day by looking at the sun in the sky：morning，noon and afternoon.

Around the year 1400，people began to use the hourglass(沙漏)．It was made of glass with some sand in it.It was wide at both ends，but narrow in the middle.The sand ran from one end to the other in one hour.At the end of every hour，people turned the glass over and began again.Hundreds of years later，a machine called clock was invented.

After that people made small clocks，so that they could carry them in their pockets.Then during World War Ⅰ，men started wearing their watches on their wrists.It was easier to tell the time.Now almost everyone wears a wrist watch.

1.How could people know the time a long time ago？(不超过10个词)

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2.What was the hourglass made of？(不超过15个词)

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3.What does the writer mainly want to tell us？(不超过10个词)

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