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I have received an offer letter, in which the offeror states the terms and conditions. I understand that this expression (expression 1) is grammatical: "The terms and conditions are stated in the offer letter". Expression 1 is in passive voice ("are" is an auxiliary verb; "stated" is a passive verb), and I think expression 1 grammatical because whenever I read the offer letter, the offeror in the offer letter does state the same terms and conditions. On the basis of the above analysis, is this passive expression (expression 2) grammatical: "The terms and conditions are stated by the offeror in the offer letter"? Thank you in advance.
Comments  

# 1 "The terms and conditions are stated in the offer letter".

#2 "The terms and conditions are stated by the offeror in the offer letter"?

They are basically identical passive sentences. The only difference is that #1's agent is understood in the context and therefore omitted. It is more idiomatic whereas #2 has the agent unnecessarily identified which makes the sentence unnatural.