Final answer:
Constraining is not a management function; the main functions include planning, controlling, directing, and organizing.
Step-by-step explanation:
The function that is not a management function is c) constraining. Management functions generally include planning, controlling, directing, and organizing. These are considered the core functions that contribute to the effective and efficient running of an organization. Constraining is not typically viewed as a distinct management function, as the aim of management is to optimize and leverage resources, not necessarily to constrain them, although managers may set boundaries and limitations as part of their strategy.