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来源:雅诚德英语网
Heavy water is heavy because the hydrogen in it weighs twice as much as ordinary hydrogen (it has a proton and a neutron in its nucleus, instead of just a proton).
重水之所以重是因为水中氢的重量是普通氢的两倍(它的原子核中有一个质子和一个中子,而不仅仅是一个质子)。