“删除冗词”是William Strunk和E.B. White在其经典之作《The Elements of Style》中，提出的一个基本创作原则。铭记这个写作原则，可以为正在准备论文投稿的您，提供极大的帮助。而要消除文句中的冗词，让每一个词都有意义，有好几种方式，我们可以从句型It is known that开始。
虽然句型It is known that也是好文笔的一环，但是使用该句型常常会造成句子过长，有时使用不巧当，甚至会产生歧义，让读者困惑。请参考以下范例：
This result indicated that the N and O atoms of the ligand were coordinated to the metal ion. It is known that the coordination mode of a carboxylate ion to a metal can be estimated from…
有些读者可能会在读到It is known that的时候停下来，一时误以为虚主语it指代的是carboxylate iron，因为它是离it最近的单数名词。为避免此误解以及精简句子，原句可改为：
This result indicated that the N and O atoms of the ligand were coordinated to the metal ion. The coordination mode of a carboxylate ion to a metal can be estimated from…
总结以上的虚主语之常见谬误，我列举了以下几个范例。
原句：It is known that most analogs with this general formula exhibit cross-resistance.
改句：Most analogs with this general formula are known to exhibit cross-resistance.
或是：Most analogs with this general formula exhibit cross-resistance.
原句：It is known that the two species are anionic and that they form an ion pair with an organic cation.
改句：The two species are anionic, and they form an ion pair with an organic cation.
原句：It is known that Henry’s law constants have temperature dependence.
改句：Henry’s law constants depend on temperature.
原句：It is known that the translational diffusion of the molecule is much faster than that predicted by the Stokes–Einstein equation.
改句：The translational diffusion of the molecule is much faster than that predicted by the Stokes–Einstein equation.
原句：It is generally thought that its therapeutic effect is triggered by…
改句：Its therapeutic effect is generally thought to be triggered by…
原句：It should be noted that the former method has an advantage over the latter.
改句：Note that the former method has an advantage over the latter.
或是：The former method has an advantage over the latter.
原句：It is also reported that diffusion is exceptionally slow.
改句：Diffusion is reported to be exceptionally slow.
或是：Diffusion is exceptionally slow.
当您因为期刊字数要求，必须缩减摘要字数时，这些简单的修改会非常有帮助。因此，您不妨在投稿论文前，快速浏览文章中的it be句型，并做适当修改，特别是紧跟在单数名词后面的it。
参考来源：
Strunk, William, and E.B. White, The Elements of Style, 3d ed. (New York: Macmillan, 1979), p. 23.
For some excellent examples of the usefulness of expletive constructions, see what Joseph M. Williams refers to as “it-shifts” in Style: Toward Clarity and Grace (Chicago: University of Chicago Press, 1990), p. 72.
For a more-extensive discussion of this problem, and other problems with “it is,” see Bryan A. Garner, Garner’s Modern American Usage, 3d. ed. (Oxford: Oxford University Press, 2009), p. 484.
