---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.
—Good morning, class! —___________.
I don’t know the answer. Can you tell me the ______ answer?
The weather report says it will rain tomorrow, so bring an ______with you.
Mark isn't coming to the concert ______ he has got too much work to do.
The girl is very friendly. She often ______ at me when I see her.