Which of the following best captures the meaning of "militate"?

The term "militate" refers to having a specific effect or influence, often in a negative or opposing sense. This aligns well with the meaning of "to have an effect against," suggesting that it implies a force or factor that acts in opposition to something else.

In this context, "militate" is frequently used in discussions about how certain factors can work against a particular outcome or idea. For example, when saying that a certain condition militates against success, it means that condition hinders or obstructs the pathway to success.

The other options present meanings that do not align with the core definition of "militate." Providing exclusive rights suggests ownership or access, remaining calm and settled pertains to emotional or physical states, and signifying something is harmless implies a lack of threat—none of these correspond with the idea of exerting an opposing influence, which is central to the meaning of "militate."