What characterizes an adjustable rate mortgage (ARM)?

An adjustable rate mortgage (ARM) is characterized by the rates that adjust based on a prescribed calculation. Unlike fixed-rate mortgages, where the interest rate remains constant for the entire term of the loan, ARMs start with a lower initial interest rate that is fixed for a specific period. After this period, the interest rate fluctuates based on a specific index and margin, which can lead to changes in monthly payments.

This feature allows borrowers potentially to benefit from lower initial rates during the early years of the loan but also involves the risk of rising payments if interest rates increase. Therefore, option B accurately reflects the fundamental nature of ARMs, highlighting the dynamic aspect of their interest rates rather than a stable or fixed rate situation.