Answer:
B. For thousands of years, Asian civilizations were separated from
Europeans and Africans.
D. They both have natural barriers like the Himalayas.
Explanation:
The reasons East and South Asia form a region is because of the following:
1. For thousands of years, Asian civilizations were separated from
Europeans and Africans - Over the years in human history, Europe and Africa had little or no contact with East and South Asia. Thereby, the region developed its civilizations and ethnic groups in its way or pace. This also made the region not form part of the advancing and conquering powers of the Mediterranean empires such as Rome, Egypt, Greek, etc.
Also, they both have natural barriers like the Himalayas which joined the two regions together as the Himalayas is formed between many countries in the area, including present-day China, India, Bangladesh, Nepal, etc
