Internally,Mongkut and Chulalongkorn Saved Thailand from Being Dominated by Imperialistic

 Internally,Mongkut and Chulalongkorn saved Thailand from being dominated by imperialistic Europeans through which of the following?

A) Politically,Thailand was divided into small states with appointed governors loyal to the king.
B) Economically,Thailand was closed to foreign trade to all European nations.
C) Culturally,it gave up areas to European nations to create a more ethnically defined nation.
D) Having created a modern military,Thailand was able to defeat both French and British invasions.
E) Religiously,it allowed missionaries to establish themselves in Thailand.