Traveling is a good way to           different cultures and broaden the mind.

In the past few years, sea ice ____ in the Arctic as a result of global warming.

—You speak very good French!                                                                 —Thanks. I ______ French in Sichuan University for four years. 

I ran across David while walking along the street yesterday. I ________ him for three years.

After the examination，my teacher told me that failure _______the mother of success.