Which one of the following institutions is NOT a part of the World Bank Group?

The World Bank Group consists of five international organizations: IBRD, IDA, International Finance Corporation (IFC), Multilateral Investment Guarantee Agency (MIGA), and International Centre for Settlement of Investment Disputes (ICSID). 'The Bank for International Settlements (BIS)', headquartered in Basel, Switzerland, is an independent organization of central banks established in 1930 and is not part of the World Bank Group.