四、語法填空。
閱讀下面短文，在空白處填寫1個適當的單詞或括號內所給單詞的正確形式。
There is a small thing we use every day. We usually put it in the bathroom. Without it, we might have tooth 1.______
problems
(problem). Can you guess what it is? Yes, it's the toothbrush. But do you know anything about 2.______
its
(it) history?
According to some research, before toothbrushes appeared, the ancient Chinese people used some small tree branches (樹枝) 3.______
to clean
(clean) their teeth. About 800 years ago, people made a kind of brushes with pig hair and bamboo. It might be 4.______
the earliest
(early) form of toothbrushes in the world. As time went by, the forms of toothbrushes changed. For example, people 5.______
chose
(choose) horse-tail hair instead of pig hair 6.______
because
pig hair was too hard. Imagine that you travel back to hundreds of years ago and brush your teeth 7.______
comfortably
(comfortable). It sounds fantastic, doesn't it?
In 8.______
the
15th century, the Chinese toothbrush found its way into Europe. It became popular among local people soon. The 9.______
invention
(invent) of toothbrushes was not as famous as that of paper-making, but it was very 10.______
useful
(use) in our daily life. Today we have a good habit of brushing teeth. We should thank the ancient Chinese for it.
