21.Here’s one of the best ways to protect your skin—_____ too much sunshine.
| A．not to absorb | B．not having absorbed |
| C．having not absorbed | D．don’t absorb |
17. The boy sat at the top of the hill, looking at the valley ______.
| A．under | B．above | C．up | D．Below |
16. I have never heard such a beautiful song _____.
| A．ago | B．before | C．later | D．Just |
15. With the development of West China, many technicians are _____ needed there in recent years.
| A．many | B．bad | C．badly | D．Well |
14. China has a lot of coal and oil, and it is rich in other rare minerals ______.
| A．as well | B．also | C．either | D．Neither |
13. --- How long has he been in the army?
--- Oh, he joined the army as far ____ as 1997.
| A．ago | B．away | C．from | D．Back |