2. 外语
  3. Dalton wondered why the heavier and lighter gases in the atmosphere did not separate as oil and water do. He finally concluded t

Dalton wondered why the heavier and lighter gases in the atmosphere did not separate as oil and water do. He finally concluded t

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问题     Dalton wondered why the heavier and lighter gases in the atmosphere did not separate as oil and water do. He finally concluded that the constituent【C1】______must exist in the form of  【C2】______particles or atoms and that these【C3】______be completely mixed together in the【C4】______. This threw a new light in【C5】______laws of definite proportions. It was  【C6】______necessary to suppose that the atoms【C7】______combine  into small groups of uniform【C8】______and so form more complex substance;【C9】______the mystery of this law was【C10】______. Dalton suggested, for example, that carbon monoxide【C11】______formed by the one with one【C12】______of atoms of carbon and oxygen,【C13】______carbon dioxide results from a single【C14】______of carbon uniting with two atoms【C15】______oxygen. Assuming this to be true,【C16】______the definite proportions of Prout’ s law (【C17】______all chemical compounds the different constituents【C18】______enter in unvarying  proportions) would naturally【C19】______the relative weights of the many【C20】______kinds of atoms.
【C11】
选项 A、must
B、been
C、were
D、is
答案D
解析 因为是表示一般规律，主语是carbon monoxide“一氧化碳”，又是单数，所以用is这个词。
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大学英语四级

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