选词填空
请根据所给句子的内容，从下面方框中选出适当的词，并注意其正确形式。每空一词，每词限用一次。

she  five note  increase  billion  fall  walk  sudden  close down  two

Wendy_____ off her bike and hurt her right arm last week .
My American friend Lucy is coming to China, and I plan to show ____ around our city.
I haven’t been to Nanjing, but my father has been there _____.
The farmers were working in the field and ______ it began to rain.
I think three _____ of restaurants are using bad oil.
I saw her_____ into the school library just now.
My uncle lost his job because his company_______ last month.
_____ of people all over the world watched the football match last night.
I think making _____ in class is a good way to learn English well.
Do you think the ______ population is the biggest problem in the world ?