The statement that accurately compares public debt to intragovernmental debt is:
"Public debt is securities issued by the Treasury to investors while intragovernmental debt are loans within the federal government from the excess funds of other agencies."
This correctly distinguishes public debt, which is debt owed to external investors, from intragovernmental debt, which is the debt that one part of the federal government owes to another part, typically involving trust funds like Social Security.