A prescriptive easement is proven by a

A prescriptive easement is established through open, notorious, continuous, and adverse use of another’s land for a statutory period (in Massachusetts, typically 20 years).

To legally recognize and establish the easement, the claimant must usually bring a quiet title action in court. This court proceeding clarifies ownership rights and confirms the existence of the easement.

A (deed): not applicable since prescriptive easements arise without written agreements.

C (abstract): summarizes recorded documents but would not establish prescriptive rights.

D (title policy): insures title, does not prove an easement.

Thus, the correct answer is B: quiet title action.