Not having worked out the problem, ______ leave the office.
16. The story that follows _____ two famous characters of the Rocky Mountain gold rush days.
15. An awful crash between an express train and a bus _____ , however, occur the other day in Russia.A. does B. did D. has to D. had to
14. Many businessmen attended the Boao Forum (博鳌论坛) because they knew what _____ from the forum.
13.The reason is____________ smoking tobacco causes illness.A. why B because C. that D. because of
12. Mr. Johnson enjoyed _____ by working in the factory again because he always hates _____ while staying alone at home all day long.