There is a small but important thing in our daily life.We usually put it in the bathroom and use it（1）

at

at

least twice a day.If you refuse（2）

to use

to use

（use） it，you might have tooth problems.Can you guess what it is？Yes，it's the toothbrush.But do you know anything about（3）

its

its

（it） history？Do you wonder how the ancient people brushed their teeth？
    According to some research，people have been using tools to clean their teeth for much，much longer.Before toothbrushes （4）

appeared

appeared

（appear），the ancient Chinese people cleaned their teeth with some small tree branches（樹枝）.About 800 years ago，people started to make a kind of brushes with pig hair and bamboo.It might be（5）

the earliest

the earliest

（early） toothbrush in the world.As time went by，the forms of toothbrushes changed.For example，people chose horse-tail hair instead of pig hair （6）

because

because

pig hair was too hard.Imagine that you travel back to hundreds of years ago and brush your teeth（7）

comfortably

comfortably

（comfortable）.It sounds fantastic，doesn't it？
    Around the 15th century，the Chinese toothbrush（8）

was brought

was brought

（bring） into Europe.It became popular among local people soon.Then a kind of new material，nylon，took the place of the natural animal hair.In 1954，the first electric toothbrush was invented in Switzerland.
    The（9）

invention

invention

（invent） of toothbrushes was not as famous as that of paper-making，but it was very （10）

useful

useful

（use） in daily life.Today we have a good habit of brushing teeth.We should thank the ancient Chinese for it.