The most powerful state to emerge in mainland southeast asia before the sixteenth century was

The correct answer is Angkor. Angkor is known to be the capital city of the empire Khmer. This is also known and recognized as Yasodharapura by which it flourished in the 9th until the 15th century. It is considered to be one of the most important archaeological sites found in South east asia.

. political or economical policy that isolates a country from participating in international relationships. it has been suggested that the united states participates in isolationism because of its lack of involvement in particular wars or alliances.

this is a good question! i'll do some research and come back when i have the answer!