Check my answer?

which factor enabled japan to pursue a policy of isolationism in the seventeenth century?
(my answer is the ***)

a. as a series of islands, japan did not share borders with other countries

b. korea and japan forged and alliance, which deterred interactions with other countries

c. monsoons made japanese seas impassible most of the year

***d. the emperor centralized power, giving him control of trade and military forces.

D. The emperor's centralized power, giving him control of trade and military forces. Coming after the period of "warring states" and great economic and cultural trade with both Portugal and Spain, the shogun of the Tokugawa (the last military government the Japan had) chose to isolate the the archipelago from outside influence, believing that the colonial and religious influence of the Iberian countries was a treat to the stability of the shogunate and the peace in the Japanese Islands.