I believe the answer is A) Japan's ruler did not allow them to conduct business anywhere else.
Just took the test and B) is wrong for sure.
Explanation:
the pf text book says: " Apart from the Dutch, who were allowed only on the small island of Deshima in Nagasaki, the only foreign trade was with the Koreans and Chinese."
I would assume the word "allowed" means that the Japanese ruler at the time only allowed them to do commerce there.
