Which of the following is an officer's Area of Concentration (AOC)?

An officer's Area of Concentration (AOC) refers to their specific branch or specialty within the Army, which defines their primary role and responsibilities. In this case, the numbers and letters represent different AOCs within the Adjutant General's Corps.

42B refers to Human Resources Officers, 42C designates a position in Human Resources Management, and 42H is for Human Resources Plans and Operations Officers. Each AOC serves a distinct function, yet they all fall under the broader umbrella of human resources within the Army.

The option indicating "all of the above" is correct because it encompasses the full range of AOCs listed, acknowledging that each contributes to the operational capabilities and needs of the Army's human resources function. Therefore, selecting this option correctly recognizes that all the provided AOCs are relevant and valid within the scope of officer specialties.