The correct answer is: "I. national defense, II. Social Security, III.personal incomes taxes".
One of the competencies of the federal goverment is to be in charge of a joint defense strategy, which constitutes its highest expenditure.
The main transfer programs are connected to the Social Security system, that provides income for those who cannot earn for a living on their own. The most important transfer is the unemployment benefit. Also there are transfers for people who cannot work due to an illness.
Public funds are mostly raised from taxes, and the most important is the income tax, a proggresive tax charged to the working population. Progressive means that depending on their total income level, different rates are applied to each individual.