Half of all plant-based medicines are derived from plants in tropical rain forests around the world. In fact, 70% of medicines for cancer come from rain forest plants. Aspirin and many other drugs come from rain forest plants, too. These plants are valuable in that they are composed of unique chemicals that have been synthesized (    A    ) millions of years. The wide diversity of plant species found in rain forests provides scientists a great resource for many new medicines. However, scientists have tested only one percent of rain forest plants.

How are plants in the rain forest used to make drugs? When a plant with possibilities is discovered in the rain forest, it is harvested and then analyzed for its chemical structure. Chemical compounds are extracted from the plant and broken (    B    ) into components that are scientifically investigated (    C    ) their potential use. Chemists compare the molecules in the tropical plant compound to the molecular structure of other known chemicals. The plant molecules may be altered to produce the required effect.

Even if the plant molecules have potential as a drug, the plants might not be available (    D    ) quantities sufficient to produce enough of the necessary chemicals to make a medicine. Or, in some cases, there is enough of a particular compound, but it has some toxic side effects. In such cases, drug development companies are using synthetic support to further examine the chemicals they need from the rain forest plant. The natural product from the rain forest plant is used as a model and then modified to reduce toxicity and/or improve the potency of the compound (    E    ) a result of this process, new chemicals can be developed to be used as a medicine.

The process of getting a plant from the rain forest to the market as a safe and effective drug is long and costly. It could cost a company more than $\$$800 million and take as many as 12 years to produce a successful drug. For every 10,000 to 20,000 tropical plant compounds discovered and tested, only one is approved and makes it to the market.

• 〔1〕 空所(A)~(E)に入る最も適切な英語を選択肢から選び、記号で答えなさい。但し、同じ選択肢を重複して使用してはならない。(文頭にくるものも、すべて小文字で表記してある。)
  • (ア) as
  • (イ) at
  • (ウ) down
  • (エ) for
  • (オ) from
  • (カ) in
  • (キ) of
  • (ク) on
  • (ケ) over
  • (コ) to
• 〔2〕 本文と内容が合致するものを、選択肢から2つ選び記号で答えなさい。
  • (ア) Rain forests are precious because ingredients from tropical plants may have medicinal value.
  • (イ) Only one percent of tropical plants have the potential to be produced as a medicine for treating cancer.
  • (ウ) The key to producing a new medicine from a tropical plant is that some chemicals in the plant should cause toxic side effects.
  • (エ) One of the conditions is that the amount available of the plants has to be large enough to produce a new medicine.
  • (オ) Each plant-based drug may contain 10,000 to 20,000 chemical components which are carefully examined by scientists.