We use indefinite pronouns to refer to people and things when we do not know or do not need to mention who or what we are talking about.

当我们不知道或没有必要说明所谈论的人是谁或是什么事物时，我们就用不定代词来指代人或物。

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Mr. Plumeri: The risk for us is to not establish ourselves in the business community in China and Hong Kong, and let them know who we are, what we do and what we offer.

WSJ: Managing in Asia: Willis Is Primed for Developing Asia

And my visits are just a simple way of saying yes, in fact, we see you, we know who you are, we value what you do, and we couldn't be here, wouldn't be here without you.

WHITEHOUSE: THE WHITE HOUSE

Our clients know who we are and what we do.

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