To "void" something means to:

To "void" something means to invalidate it, which is why the chosen answer is correct. The term "void" originates from a legal context, where it refers to declaring something as having no legal effect or being null and without value. For instance, if a contract is voided, it means that the contract is treated as if it never existed, losing any binding force or obligations that may have been established.

Other choices, while related to the concepts of validity, legitimacy, or effectiveness, convey the opposite or unrelated meanings. Confirming validity suggests that one is affirming something's worth or correctness, enhancing effectiveness implies making something more effective or improving its functioning, and supporting legitimacy involves providing backing or justification for something's authenticity or legal standing. These concepts do not align with the definition of "void," thereby reinforcing why the selected answer accurately describes its meaning.