The correct answer is: B. Opportunity cost approach.
The opportunity cost approach is a method of valuation that considers the value of the next best alternative that is forgone when a decision is made. In the context of human resource valuation, the opportunity cost approach would value a worker based on the salary they could earn in their next best job.
The replacement cost approach is a method of valuation that considers the cost of replacing an asset. In the context of human resource valuation, the replacement cost approach would value a worker based on the cost of hiring a new worker with the same skills and experience.
The historical cost approach is a method of valuation that considers the original cost of an asset. In the context of human resource valuation, the historical cost approach would value a worker based on the cost of hiring them, which may be significantly less than their current salary.
None of the above is the correct answer because it does not specify which approach is adopted for the valuation of human resource according to economic concept.