4. the largest proportion of federal revenues comes from
a. excise taxes. b. personal income taxes. c. borrowing. d. social insurance taxes.

Well, The largest proportion of federal revenue comes from the personal income taxes. From more than 60 years, It has been the largest source of the federal revenue. Around 43% of the federal revenue comes from Income tax and around 35% revenue comes from Payroll taxes. Common people give more contribute to the economy.