Which of the following best defines "fit for duty"?

The definition of "fit for duty" encompasses both the physical and mental capabilities required to effectively perform assigned duties in a job. This concept is crucial in ensuring that individuals can meet the demands of their roles, particularly in fields where both physical and mental resilience are essential, such as law enforcement, healthcare, and emergency services.

Option C encompasses the entirety of what it means to be "fit for duty" since it takes into account not just one aspect of a person's abilities but rather a comprehensive evaluation of both physical and mental readiness. This dual assessment is necessary because employees may face scenarios that challenge them both physically and mentally.

In contrast, the other options are limited in scope. Focusing solely on a mental capability assessment, a physical fitness test, or a background investigation does not provide a complete view of an individual's readiness to perform their job responsibilities, as these may overlook critical areas that contribute to overall effectiveness and safety on the job. Thus, the selection of option C as the most accurate definition reflects an understanding that suitability for duty involves a holistic assessment of capabilities.