Which of the following is a characteristic of a mortgage payment plan?

A mortgage payment plan typically features fixed monthly installments, which illustrate a structured repayment schedule. This characteristic is fundamental to mortgages as it provides borrowers with predictability in their budget management. Each monthly payment is primarily made up of both principal and interest, allowing the borrower to gradually pay down the loan amount over time, which is essential for amortizing the debt fully by the end of the loan term.

In contrast, other options describe payment structures that do not align with standard mortgage agreements. For instance, irregular payments or payments only made at the end would undermine the predictable repayment model that mortgages establish. The fixed monthly structure is a cornerstone for managing large debts like home loans, making option B the defining characteristic of a traditional mortgage payment plan.