What is the single largest source of revenue for the federal government?

Usually this is mostly from personal income tax depending partly on the population of the country and the larger the population the greater the income. While corporations also pay some tax, they also have many exemptions and loopholes, more than the ordinary person. Corporations also often receive large amounts of tax money to pay for infrastructure that they need such as the government building and paying for new mining towns in remote areas to service new mines. 

It’s obvious the asnwer is false