What Is a Prime Reason That the IRS Has Found

What is a prime reason that the IRS has found it difficult to obtain information needed to examine the transfer pricing scheme of foreign parents with U.S. subsidiaries?

A) The information is held by the foreign parent, which is beyond the jurisdiction of the U.S. taxing authority.
B) Since transfer pricing is not a significant issue to multinational corporations, little information about it exists.
C) United States does not have tax treaties with the most important countries involved in foreign direct investment in this country.
D) Computer systems have not been adapted to receive the data from companies in foreign countries.