C. was still learning                    D. has been learning

4. By the end of last week, he ________ in the company for 10 years.

A. had worked                        B. had been working

C. will have worked                    D. would have worked

5. Not until then did people know that he ________ important military information to the enemy for a long time.

A. sold        B. would sell        C. had sold        D. had been selling