Which of the Following Statements Regarding a Foreign Person's U

Which of the following statements regarding a foreign person's U.S. tax consequences is true?

A) Foreign persons must be physically present in the United States before any U.S.-source income is subject to U.S. income or withholding tax.
B) Foreign individuals may be subject to U.S. income tax but foreign corporations are never subject to U.S. income tax.
C) Foreign persons are only subject to U.S. income or withholding tax if engaged in a U.S. trade or business.
D) Foreign persons are potentially subject to U.S. withholding tax on U.S.-source investment income.