无依附的动词不定式 见 unattached infinitive, present participle infinitive
是用纯不定式还是用现在分词？见 see sb. do/doing, hear , feel
分裂不定式见 split infinitive
infinitive/gerund
The function of Louis Sullivan's architecture was providing large uninterrupted floor areas A B
and to allow ample light into the interior. (TOEFL) C D
试题要求将动名词 providing 改为动词不定式 to provide。但是我不理解为什么要作这种更改。难道动名词不可以充当表语(主语补语)吗？请看下面的例句：
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My hobby is swimming. 我的爱好是游泳。
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Her first job had been selling computers. 她的第一个工作曾是销售计算机。
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Seeing is believing. 百闻不如一见。
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The only thing that interests him is dancing. 他唯一感兴趣的事是跳舞。
知道动词不定式和动名词都可以充当表语(主语补语)，这只是个一般的知识。在这个基础上还需要一些更具体的知识。比如，在 the function 充当主语时，其表语(主语补语)只能由动词不定式来充当，而不能由动名词来充当。请看下面的实例：
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"Did the audience participate in the play?"
"Yes, those actors ____ to involve the audience."
A. whom it was the function B. of whom the function was
C. whose function it was D. whose were the function (TOEFL) -
The main function of the kidneys is to purify the blood. (FWF) 肾的主要功能是净化血液。
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The function of an adjective is to describe or add to the meaning of a noun. (LDCE) 形容词的作用是描述或增加名词的意义。
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The function they perform is to maintain the established order of society. (London) 他们的职务是维护建立起来的社会秩序。