Final answer:
Barack Obama appointed Timothy Geithner as Secretary of the Treasury, a crucial role involving advising on economic issues and managing the nation's finances.
Step-by-step explanation:
As President, Barack Obama appointed Timothy Geithner to the position of Secretary of the Treasury. The role of the Secretary of the Treasury includes advising the President on financial and economic issues and managing the public finances. The selection of cabinet members, such as the Secretary of the Treasury, is an essential task for incoming presidents and requires confirmation by the Senate. When forming a cabinet, presidents often consider a range of factors, including expertise, ability, influence, and demographic representation to ensure they have an effective and representative group of advisors.