Final answer:
The time period before the forfeiture of "A's" interest can be enforced depends on the specifics of the agreement and state law, often involving a notice period such as 30 or 60 days, as seen in standard termination clauses.
Step-by-step explanation:
In the scenario where "A" acquired a house from "B" with a down payment and has made partial payments towards the balance but then ceased to make further payments, the specific time required before the forfeiture of "A's" interest in the house can be enforced depends on the terms of the agreement for sale and applicable state laws. Without specific details of the agreement or jurisdiction, it is not possible to provide a definitive answer to the question of whether the expiration period is 30, 60, 90, or 270 days. However, standard real estate contract laws often have clauses regarding default and forfeiture, with common notice periods being 30 or 60 days.
For example, if the contract includes a termination clause similar to the one provided that allows for termination after a 30-day written notice, one might infer that the expiration period for forfeiture enforcement could be 30 days. Nevertheless, without the actual agreement's terms or knowing the exact state law that applies, one cannot provide the correct selection from the options given.