MUST BE UNEQUIVOCAL
MIRROR IMAGE RULE: absolute and unequivocal acceptance of each and every term of the offer required at common law, otherwise it's a rejection and counteroffer.
Statements that make implicit terms explicit do not prevent acceptance, grumbling acceptance okay.
A request for clarification does not necessarily amount to a rejection and counteroffer.
Art2 BATTLE OF FORMS: Instead of the mirror image rule, art2 provides instead that the prosposal of additional or different terms by the offeree in a definite and timely acceptance does not constitute a rejection and counteroffer, but rather is effective as an acceptance unless the acceptance is expressly made conditional on assent to the additional terms. Whether the terms become part of the contract depends on whether both parties are merchants.
However, there are cases where, even if parties do not agree to the terms, if they begin to perform as if they have formed a contract, a contract is formed.