It’s difficult to live in a foreign country, ________ if you can’t understand the language there.

Of the three girls, Mary sang             

Cindy is a good student. She’s ________ the first to come to school. She ________ comes to school late. 

— _________ has Liu Xiang taken part in world’s competitions of 110-metre hurdles?— I’ve no idea. Let’s find it out on the Internet.

-- Is air the lightest thing in the world?-- Not            . Scientists from Zhejiang University have just developed the world’s lightest material.