12、It is because he is kind and modest ________ he wins the respect of all presents.

21. We worked hard and completed the task().

20. Once environmental damage(), it takes many years for the system to recover.

19. The red flower goes from one to()in the class

18. Two days is not enough for him to finish the work. He needs()day.

17. Therefore, other things()equal, the member of workers that employers want decreases.

16. It’s time we()the lecture because everybody has arrived.

15. The girl is()of a film star.

14. The atmosphere()certain gases mixed together in definite proportions.

13. Tom what did you do with my documents? I have never seen such a()and disorder.

12. The students were all entertained in a Mexican restaurant, at Professor Brian’s().