从每题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项。

21. John promised his doctor he ________ not smoke, and he has not smoked ever since.

　 A. might　　　 B. should　　 C. could　　 D. would.

第二节：书面表达(满分25分)

如今世界粮食短缺，价格飞涨，给部分地区造成社会动荡。假设在你校开展的研究性学习中，你们小组以“World Food Crisis”为题进行研究，现在请你代表你们小组向全体同学简要介绍你们的研究成果。主要内容如下：

注意：1. 内容包括以上要点，但不要逐句翻译

　　　 2. 字数150左右，文章开头已提供，不计入总词数

　　　 3. 参考词汇：城市化　 urbanization　 　生物燃料　 bio-fuels

　Hello, everyone,

Now I’ll tell you something about our research project The World Food Crisis on behalf of our group. As you know, food shortages have hit many countries in the world and even caused social unrest in some areas. But who is responsible for the current world food crisis? First, annual world grains output has declined because of climate change. Then lots of farmland has been lost due to the rapid development of industry and urbanization. Besides, faced with the rising energy prices, people have turned to the production of bio-fuels, which has worsened the severe situation.

Then what should we do to deal with the problem? On one hand, we should focus on the environmental protection and improve the ecology. On the other hand, strict measures should be taken to protect farmland. Of course, to build a harmonious world the developed countries should take their responsibilities to help the poor ones experiencing food shortage.

As for me, I will call on the people around me to live thriftily. And for the moment, I think, we should study hard to develop science and help solve the food shortage in the future.