次の英文を読み下の問いに答えなさい。



An American scientist has shown a link between increased production of ragweed pollen and rising temperature on earth. Lewis Ziska of the Agricultural Research Service [     ] the study. [      ] found that ragweed plants produce almost two times as much pollen now as they [      ] one hundred years ago. The study suggests pollen level could go up another one-hundred percent as temperatures continue [      ] rise over the next century.

Agricultural Secretary Dan Glickman says the study may lead to a better understanding of the effect of high carbon dioxide levels [      ] our environment and human health.  

          　
Many scientists say carbon dioxide and other gases [      ] trapping heat in Earth’s atmosphere. These gases are released when vehicles, factories and power centers burn fuels like coal, oil and natural gas. An [      ] in temperatures could raise sea levels. And it could cause serious weather changes such as flooding or periods of dry weather.

An estimated forty-million people in the United States suffer from allergies. Many have allergic reactions to [        ], produced by plants, such as ragweed. Pollen [       ]a reproductive substance produced [        ] flowering plants. It can be carried by the wind. Ragweed pollen is major cause of allergic attacks in autumn. It causes some people to have trouble breathing. Their eyes may burn and water. They may sneeze a lot.

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1. 次の[             ]に語句を一つ入れて、この記事のタイトルを完成しなさい。　
　　　地球 [     　　　 ]化で花粉症が増加か ?
2.　上の英文内の [     　　 ]に適当な語を入れなさい。
3. “ragweed” とは次の植物（スギ, 菜の花, シダ, ブタクサ, イチョウ）のうちのどれと考えられるか, 理由を付けて答えなさい。
4. アンダーラインのsentence と同じ話法の文全てにアンダーラインを施しなさい。
5. この記事で最も重要なsentenceを書き抜き、その意味を25字以内の日本文で記しなさい。