Choice "D" is correct. Agency funds are used to account for assets (such as taxes collected) held by a governmental unit (such as a county) acting as an agent for another governmental unit (such as a school district).Choice "c" is incorrect. Special revenue funds account for the proceeds of specific revenue sources that are legally restricted or earmarked to expenditures for specified purposes.Choice "b" is incorrect. Internal service funds account for the financing of goods or services provided by one department to other departments within the governmental unit on a cost reimbursement basis.Choice "a" is incorrect. Trust funds are not a fund classification identified by GASB #34. Funds held in trust would likely be accounted for in a fiduciary fund, which would account for assets held by a governmental unit in a trustee (fiduciary management) capacity (as opposed to a pure agent capacity) for others.