We first met on a train in 2010，but we both felt immediately that we ________ each other for years.

(2014·湖南十二校联考)I got an e­mail from my old friend last Sunday.Until then，we________in touch for nearly 3 years.

I ______ all day and I haven’t a penny left.

The best way to prevent the air polluting _____ , but the sky is still not clear.

--David, are you 1istening to me?--Sorry, Dad. I _______ to make sense of what the reporter said.