A core competency is

a$.$ the specific set of departmental skills, knowledge, and experience that allows one organization to outperform another.

b$.$ the planning, organizing, leading, and controlling of human and other resources to achieve organizational goals efficiently and effectively.

c$.$ a measure of how efficiently and effectively a manager uses resources to satisfy customers and achieve organizational goals.

d$.$ a measure of the appropriateness of the goals an organization is pursuing and the degree to which the organization achieves those goals.

e$.$ the ability to analyze and diagnose a situation and to distinguish between cause and effect.