In the context of human resource management, human capital refers to the
选项：

A:wages, benefits, and other costs incurred in support of HR functions in an organization.
B:cash, equipment, technology, and facilities that an organization uses.
C:tax-deferred value of an employee's 401(k) plan.
D:organization's employees, which add economic value to the company.
E:total budget allocated to the HR department in an organization.