Under US Tax Law, What Is the Relationship Between Foreign Tax

Under U.S. tax law, what is the relationship between foreign tax credits and the different categories of foreign source income?

A) FTC from one category can offset taxes owed on other categories.
B) Excess FTC from one category can be carried forward to offset future U.S. taxes payable on another category.
C) Excess FTC from one category can be carried back to offset U.S. taxes paid on another category in the prior year.
D) None of the above