______ difficult the problem was, he tried his best to solve it.

Beijing government puts more than 700 million yuan to increase its green space this year,____________ doubles the money provided last year.

— ____ visited the Shanghai World Expo is sure to tell you the place is worthy ____ twice． — You can say that again．

 I was about to leave my house________the phone rang. 

 —Tom has passed the final exam.—______! He never really worked hard before.