Bicycling is a good exercise;________ it does not pollute the air.

– Who ran most__________ at the sports meeting in your class? -- Li Ming did. He won the first place.

The Internet is really useful  to us. We can ________ find the information we need.

—Do you think yesterday’s math problem was difficult? —Yes. I could ________ work it out. 

— The girls are talking about the art festival__________ .— Yes. They have so many fun things to share.