Which of the following statements regarding income sourcing is not correct?

a.U.S. persons are not concerned with source of income because all their income is subject to U.S. tax under a worldwide system.

b.Concerning the foreign tax credit, most U.S. persons benefit from earning low-tax foreign-source income.

c.Foreign persons generally benefit from avoiding U.S.-source income classification.

d.Foreign persons may be subject to tax on U.S.-source income without regard to their actual presence in the United States.