Concept:Labour mobility between different grades or levels of occupation is known as vertical occupational mobility.
Explanation:When a worker moves from one grade to an entirely different grade, the status and level of the job changes.
This type of movement is not merely a change of employer or workplace, but a change in rank or hierarchy.
For example, a clerk becoming a manager or a school lecturer becoming a college lecturer represents a shift between different grades.
Such movement is called vertical occupational mobility.
Horizontal occupational mobility would involve changing jobs at the same grade, while geographical mobility involves moving to a different location.
Answer:C. vertical occupational mobility