Psychological is the answer. Hope this helps.
Answer: Geographic barriers hindered travel and trade prior to the establishment of the Silk Road trade routes. Multiple civilizations were isolated by mountains and deserts making trade next to impossible.
Explanation:
(3) People in North Africa, Europe, and Asia were affected by the disease.
Answer:
Secretary of Commerce
Explanation:
Prior to becoming President, Herbert Hoover was Secretary of Commerce and helped to develop many of the systems that are used still to regulate the airwaves.
