According to the article titled “can korea be reunited,” what is the biggest obstacle to the unification of north and south korea? a. they do not share a common border. b. they speak different languages and have very different cultures. c. they do not have a common history as a unified state. d. they have very different political systems and systems of government.

The correct answer is D. They have very different political systems and systems of government.
North Korea is considered to be a dictatorship because it has a ruler for life who has absolute authority. On the other hand, South Korea is a democratic republic, with a president who rules along with his government. 
A is incorrect because they do share a common border, their language is quite similar, which is why B is incorrect, and they were once a single state, which is why C is not correct.

Idon't bro i wish i could i'm so sorry

Yes it does it sure does me later