Which of the following represents an obligation that can lead to default?

The correct choice is the failure to make mortgage payments, as this represents a significant obligation that can lead to default on a loan. When a borrower signs a mortgage agreement, they commit to repaying the loan according to specified terms, which typically includes making regular monthly payments. If these payments are not made, the borrower risks being in default, which can initiate foreclosure proceedings and result in the loss of the property.

In contrast, paying property taxes on time, adhering to a lease agreement, and making timely insurance payments are examples of fulfilling obligations rather than failing to meet them. These actions do not lead to default; instead, they are practices that help maintain ownership of a property and protect the interests of all parties involved. It is crucial for homeowners to keep up with their mortgage payments above all else, as this directly impacts their financial standing and ownership rights.