I think the answer is b but please let me know if it was right
Answer:
It helped with communication in secret codes
Explanation:
Did some research on the web it's D.the great rift valley
The Baltic Sea is located in Northern Europe enclosed by the northwest part of Russia, Lithuania, Latvia, Estonia, Sweden, Finland, Denmark, Poland and Germany. Around these shores of the Baltic the merchant cities formed the powerful federation known as Hanseatic League.
