---Do you know about a very popular toy--- the yo-yo(悠悠球)?---Yes. Filipinos(菲律宾人) invented it ________ accident. And it ________ helping kill animals.
There____ students in our school in 2012.
China is a great country ____ a long history.
The little boy walked in the crowed city and soon he was_______.
.____ you ____ to the park last week?
--_____ will you be back? -- In a week.