The present-day country of Bangladesh is included in Area 4.
Explanation:
1. Area 1 includes Persia, which is present-day Iran.
2. Area 2 includes Mongolia, which is a separate country.
3. Area 3 includes Korea, which is divided into North Korea and South Korea.
4. Area 4 includes India, which is where present-day Bangladesh is located.
Therefore, the correct answer is D. Area 4.
