The entry port for trade between the Indus trading centres and Mesopotamia was not Afghanistan, Ur, or Elam. The correct answer is option 'D' - None of these. Let's explore the reasons behind this answer in detail.

Indus Valley Civilization and Mesopotamia:
The Indus Valley Civilization, also known as the Harappan Civilization, was one of the earliest urban civilizations in the world. It flourished in the Indus River Valley, which is present-day Pakistan and northwest India, from around 2600 BCE to 1900 BCE. Mesopotamia, on the other hand, was an ancient region located in the eastern Mediterranean, comprising present-day Iraq, Kuwait, and parts of Iran, Syria, and Turkey.

Trade between the Indus Valley and Mesopotamia:
There is evidence of extensive trade between the Indus Valley and Mesopotamia during the Bronze Age. The Mesopotamians were particularly interested in obtaining luxury goods such as precious stones, metals, and textiles from the Indus Valley, while the Indus Valley people imported goods like copper, tin, and wool from Mesopotamia.

Entry Port for Trade:
The Indus Valley people had access to the Arabian Sea through which they could conduct maritime trade with other regions. However, the exact entry port for trade between the Indus Valley civilization and Mesopotamia is still a matter of debate among historians and archaeologists.

Possible Ports for Trade:
1. Lothal: Lothal, located in present-day Gujarat, India, is one of the most prominent archaeological sites associated with the Indus Valley Civilization. It was a major port city and is believed to have played a crucial role in maritime trade with Mesopotamia.

2. Sutkagen Dor: Sutkagen Dor, located in present-day Balochistan, Pakistan, is another possible entry point for trade between the two regions. Excavations at this site have revealed the presence of Indus Valley artifacts along with Mesopotamian goods.

3. Mohenjo-daro: Mohenjo-daro, a UNESCO World Heritage site in Pakistan, was one of the largest cities of the Indus Valley Civilization. While there is no direct evidence of maritime trade from Mohenjo-daro, its location on the banks of the Indus River suggests that it could have served as an important trading hub.

Conclusion:
In conclusion, while the exact entry port for trade between the Indus Valley trading centres and Mesopotamia is uncertain, possible options include Lothal, Sutkagen Dor, and Mohenjo-daro. The trade between these two ancient civilizations played a significant role in the exchange of goods and cultural influences.