Which of the Following Statements Regarding a Non-U

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

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