Why did the summit of the Brocken become inaccessible during Germany’s division?

Why did the summit of the Brocken become inaccessible during Germany’s division?

A. It was declared a nature reserve
B. It served as a Cold War surveillance site
C. It was damaged by landslides

Fact: During the Cold War, the Brocken summit was restricted because it was used by East German and Soviet intelligence for surveillance.

Correct Answer: It served as a Cold War surveillance site