16．
It's about TimeDo you know what time it is？If you do，you probably are looking at a clock or Long ago，people didn't have clocks or watches like you do．When the sun rose，they got up and when the sun went down，they went to bed．They told timeby the position of the sun in the sky．
People discovered that they could use a stick and the sun to tell time．This was called a shadow clock．They put a stick in the ground，pointing straight up．The direction of the stick's shadow and how long or shortit was told them the time．
A better kind of shadow clock was called a sundial．Sundial had a pointer and a base．The pointer cast a shadow on marks around the base．People could tell time by reading the marks．
But shadow clocks were not good for telling time on cloudy days or at night．
One kind of clock that didn't need the sun was a water clock．A water clock was container with a tiny hole in the bottom．Water would steadilydropout of the hole．Marks on the inside of the container showed the time．It took one hour for the water to go down one mark．
Another kind of clock that didn't need the sun was a candle clock．You would know the time by how much of the candle had melted（熔化）．The candle had marks down its side to show the hours．
Sometimes people used candle clocks as alarm clocks．They put a nail（釘子）in the candle at the time they wanted to wake up，hanging a shoe on the nail．When the candle melted down，the nail fell outand the shoe hit the floor with a BANG!
Now there are all kinds of timepieces，from tall grandfather clocks to watches we wear on our wrists（手腕）．Most clocks run on electricity from batteries．
There are many more types of clocks，too．Clocks hang in and on buildings．Clocks are everywhere!
61．Did people have clocks or watches like you do long ago？No．/No，they didn't
62．What did sundial have？Apointer and a base
63．How long did it take for the water to go down one mark in water clock？One hour
64．How would you know the time when you use a candle clock？By how much of the candle had melted
65．What does the writer want to tell us？The changes/types of the clock．
