According to the article titled “can korea be reunited,” what is the biggest obstacle to the unification of north and south korea?

I have not read about the said article but maybe this can be of help. One of the biggest challenge for the unification of North and South Korea would be the  incompatibility of governments between the North and South. The two are polar opposites. Hope this helps. Have a nice day.

The answer is d if you are on edgenuity. 

Answer islamic scholars made advancements in technology, literature, philosophy, mathematics, astronomy, and the arts during this time period;