Final answer:
The correct answer is option a. The correct answer for transforming an offer into a contract is Acceptance, which is a key step in forming a legally binding agreement and may include confirming various employment terms.
Step-by-step explanation:
In the context of contract law, the affirmative response necessary to transform an offer into a contract is Acceptance. When an offer is presented, the acceptance of that offer must be communicated by the offeree to the offeror to create a legally binding contract. This acceptance confirms the terms of the offer, and may involve additional steps such as confirming the starting dates, salary negotiation, and agreeing on other terms of the employment contract.
Acceptance of a job offer, for example, is not merely saying 'yes' but is typically followed by the negotiation of the detailed terms of the employment. This could be an illustration of how contractual principles apply in the real world. It's worth mentioning that if the offeree modifies the terms of the offer in their acceptance, this is not an acceptance but a counteroffer, which the original offeror can then choose to accept or reject.