偶然在本网看到一个网友提问的句子:
Ihave a key to open the door.
https://www.cpsenglish.com/question/28770
我也查了一下类似问题的解答，发现大伙常见觉得keyto opening the door 准确，由于to 是介词。我感觉Ihave a key to open the door.这个句子没问题，这里是不定式的使用方法。不知大伙有哪些怎么看？
I have a key to open thedoor.的说法是现代英语中容易见到的使用方法，应该没错。这里to open the door 为不定式，表示目的。I have a key toopen the door with. 的说法也符合语法，但极少有人如此用了。a key to opening the door的使用方法也是正确的，也在常见用，比如：Please realizethat your creativity is a key to opening the door of the Fun Department.
经查，《牛津英语使用方法指南》一书的102（3）词条，碰巧对网友的这个问题做出知道释：
102（3）purpose:a key to open the door
An infinitivecan be used after a noun, or an indefinite pronoun like something, to explainthe purpose of a particular thing: what it does, or what somebody does with it.The noun or pronoun can be like the subject of the infinitive.
Have you got akey to open this door?
It was a warto end all wars. I'd like something to sTOP my toothache.
以上部分为该书的原文。
请注意我感觉当key不表示钥匙，而表示“重点”等类似含义时，后面的to为介词，一般后接名词或动名词。比如：The key towriting fiction is to make something that you would want to read. （free dictionary例句）
现另提供几个语料库的例句供参考：
1. People should have a keyto open the door to enter the house.
2. Maggie used the entrancekey to open the door.
3. You don't need a key tolock most doors from the inside.
