The main idea of Paragraph 2 is that______. In order to help to form shiny crystals of diamonds the carbon needed______.

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问题 The main idea of Paragraph 2 is that______.
In order to help to form shiny crystals of diamonds the carbon needed______.

选项 A、to act as a catalyst
B、to be in different forms
C、to have a pressure chamber
D、to be dissolved in a melted metal

答案D

解析 本题是细节题。根据文章第6段最后两句话:The idea was then brought forward that perhaps the carbon needed to be dissolved in a melted metal.The metal might act as a catalyst,which means that it helps a chemical reaction to take place more easily和第7段,得知制造钻石的条件之一是:carbon is needed to be dissolved in a melted metal。
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