The correct answer is C. A valid acceptance of an ordinary settlement offer must generally constitute unconditional assent to the offer's terms. Under the traditional common-law mirror-image principle, an alleged acceptance that changes, qualifies, or makes acceptance contingent upon an additional term is ordinarily treated as a counteroffer rather than acceptance of the original offer. Cornell's Legal Information Institute describes the mirror-image rule as requiring unconditional assent without modifications.

Therefore, there is no rule allowing the accepting party to add “one contingent stipulation” while still necessarily creating an acceptance. Even one material condition may prevent formation of the settlement on the original terms.

Option A is an element of proper acceptance. Option B is also correct because acceptance must ordinarily be manifested or communicated through an appropriate word, act, or other authorized method. Option D reflects the principle that the offeree—the person to whom the offer was made—is the party possessing the power to accept it. Cornell notes that an offer grants the offeree the power to accept and create a binding agreement.

Settlement agreements are contracts, so ordinary principles of offer, acceptance, consideration, authority, and mutual assent apply.

Accordingly, C is the statement that does not constitute a proper element of acceptance.