The answer to the question "Who controlled the whole area south of the Caspian sea down to eastern Arabia?" is option 'C', which is Iran. Let us understand why Iran controlled this region in detail.

Geographical Location of the Area

The area in question here is located South of the Caspian Sea and extends down to Eastern Arabia. It comprises a vast stretch of land that includes several countries such as Azerbaijan, Armenia, Georgia, Iraq, Kuwait, Saudi Arabia, Bahrain, Qatar, Oman, United Arab Emirates, and Yemen.

Iran's Historical Influence in the Region

Iran, historically known as Persia, has a rich cultural heritage, which has had a significant impact on the region's culture, language, and religion. Since ancient times, Persia has been a dominant power in the Middle East with a rich history of empire-building and cultural achievements.

In the 6th century BC, Persia's Achaemenid Empire conquered vast territories, extending from the Mediterranean Sea in the west to the Indus River in the east. This empire was followed by the Parthian and Sassanian Empires, which ruled over the region for centuries.

Iran's Role in Modern Times

In modern times, Iran emerged as a significant player in the region after the Islamic Revolution of 1979, which overthrew the monarchy and established an Islamic Republic. Since then, Iran has sought to expand its influence in the region through various means, including supporting Shia Muslim groups, establishing diplomatic ties with neighboring countries, and engaging in regional conflicts.

Conclusion

In conclusion, Iran's historical influence, cultural heritage, and strategic location have made it a dominant player in the region. Its control over the area south of the Caspian sea down to Eastern Arabia is a testament to its historical and cultural influence, as well as its modern-day efforts to expand its regional footprint.