Bank liabilities refer to the obligations of a bank towards its customers and other stakeholders. These are the financial obligations that the bank owes to external entities. One of the options provided, "nontransaction deposits", is indeed a bank liability.

Nontransaction deposits are a type of deposit made by customers into their bank accounts that are not intended for immediate withdrawal or transactional purposes. These deposits are typically held for a longer period of time and can include savings accounts, fixed deposits, and certificates of deposit.

Nontransaction deposits are considered liabilities for the bank because they represent funds that the bank owes to its customers. The bank has the obligation to repay these deposits to the customers when they demand it or when the agreed-upon maturity period expires. The bank is liable for the repayment of these deposits and must maintain the necessary liquidity to fulfill this obligation.

Nontransaction deposits are an important source of funding for banks. Banks use these deposits to invest in other assets, such as making loans or purchasing securities. The interest paid on nontransaction deposits is one way for banks to attract and retain customers. As a liability, the bank must manage these deposits effectively to ensure that it can meet the repayment obligations and maintain customer trust.

In summary, nontransaction deposits are a type of bank liability as they represent funds that the bank owes to its customers. These deposits are held for a longer period of time and are an important source of funding for the bank. Managing these liabilities is crucial for the bank to maintain liquidity and fulfill its repayment obligations.