Final answer:
John's agreement to teach as an adjunct during a professor's sabbatical is a type of temporary employment, specifically to handle responsibilities while the professor is on a study or travel leave.
Step-by-step explanation:
John's agreement to teach a statistics course on an adjunct basis during a professor's sabbatical represents b) Temporary employment. Adjunct teaching positions are typically non-permanent, part-time teaching positions at educational institutions. They are often filled by professionals who have other primary jobs or responsibilities outside of the institution.
In this context, a sabbatical is a period granted to a university professor for study or travel, traditionally every seventh year. Since John will be teaching while the regular professor is on sabbatical, this position is not intended to be a long-term, full-time, or tenure-track role. Instead, it is a temporary placement meant to fill the gap while the regular faculty member is away.