Answer:
C. the skills and knowledge that enable a worker to be productive.
Explanation:
'Human Capital' is the stock of knowledge & skills embodied in people, enabling them to perform labour of economic value. It is considered as 'capital' because skills & knowledge development to become more productive yields better income & standard of living.
Human Capital formation i.e knowledge, skills & productivity enhancement has two crucial components : Education and Health.
Options A, B, D are inapt because : Human Capital is not 'physical capital', 'financial wealth', 'machinery' ; but is rather immaterial knowledge & skill set in people.