First Principles Thinking: forward definition
A is correct. The CFA Curriculum defines a forward contract as an over-the-counter derivative in which buyer and seller agree to exchange an underlying in the future at a pre-agreed fixed price. The governing rule is customization of size, maturity, underlying details, and credit terms. The intuition is tailored hedging. Applying that definition, an OTC contract with flexible terms is a forward.
Why top distractor is wrong (CFA Curriculum-based misconception). Exchange trading with daily settlement describes a futures contract, not a forward contract.
Why remaining distractor is wrong. A forward is a firm commitment, so both counterparties are obligated; it is not a contingent claim that one side may choose to ignore.