Which of the following describes a selective factor?

A selective factor refers to a requirement that is deemed essential for a candidate to qualify for a position. This means that it is a fundamental criterion that must be met in order for an applicant to be considered for a job. For instance, if a job posting lists a specific degree or certification as a necessary qualification, that degree or certification serves as a selective factor because candidates must possess it to be eligible for the position.

The other options suggest various levels of qualifications or preferences that do not meet the standard of being essential. A preference that improves ranking may enhance a candidate's appeal but does not determine their eligibility. A non-essential qualification indicates that while it might be beneficial, it is not required, and an optional skill for application suggests that it is simply nice to have, further reinforcing the idea that it is not crucial for qualification. Therefore, the essence of a selective factor lies in its requirement to qualify for a position, making the distinction between what is necessary and what is simply advantageous.