Final answer:
The option that is not an Authorized Deposit-taking Institution (ADI) is 'Authorized Deposit-taking Institutions (ADIs)' itself, as the other options are all types of ADIs which accept deposits from the public and are regulated by APRA.
Step-by-step explanation:
The institution that is not an Authorized Deposit-taking Institution (ADI) amongst the options is Authorized Deposit-taking Institutions (ADIs) itself. An ADI is an Australian financial institution licensed by the Australian Prudential Regulation Authority (APRA) to accept deposits from the public. Therefore, options such as commercial banks, credit unions, and building societies are all a part of the ADIs because they are licensed to accept deposits. ADIs provide a range of services, including transactional accounts, savings accounts, and lending facilities such as mortgages and personal loans. Customers of ADIs benefit from the security of knowing that their deposits are protected under the Australian Government's Financial Claims Scheme (FCS).