______was it ______ they discovered the entrance to the underground palace?—-Totally by chance.

You __________ come to help me. I’ll finish it in a minute.

Ling Feng won the first prize in the national English competition and I’m glad that her efforts at last ________.

Mr. Li lent me a book last week, _____I have learned a lot about earthquakes.

________ with teens who spend much of their free time in front of TV sets, those who are physically active often have better grades.