Answer:
borrowers who don't pay back loans (also known as loan defaults) is a particularly significant risk for banks.
Step-by-step explanation:
All of the options listed are potential risks that banks should prepare for. However, borrowers who don't pay back loans (also known as loan defaults) is a particularly significant risk for banks. When borrowers default on their loans, it can result in significant financial losses for the bank, and therefore it's important for banks to have measures in place to mitigate this risk, such as thorough credit checks and loan underwriting processes. On the other hand, falling interest rates can impact the bank's profitability, and the shift towards online transactions can pose security and operational challenges, so these are also important risks for banks to consider and prepare for.