It separates North and South Korea. It was the border between them since the Korean war that was led over the unification of the country. The northeners wanted to have a fully communist Korea while the southerners wanted to have a western oriented Korea.
Winston Churchill was not worried about America since he knew they had strong industrial power
The answer is:
D - The inclusion of West Germany in NATO
I would think all of them except for 2 and 5,
hope that was what u were asking and hope I helped:) have a good night