The correct answer is option 'A': Nile.

The Nile River was indeed the lifeline of Egyptian civilization. It played a crucial role in the development and sustenance of the ancient Egyptian civilization for several reasons. Let us explore these reasons in detail:

1. Geographical Significance:
- The Nile River is the longest river in Africa, stretching over 6,650 kilometers (4,130 miles). It flows through eleven countries, including Egypt.
- The river originates from two main tributaries: the White Nile, which originates from Lake Victoria, and the Blue Nile, which starts from Lake Tana in Ethiopia. These tributaries merge near Sudan's capital, Khartoum, and continue northward as the Nile River.
- The Nile River enters Egypt near the city of Aswan and flows northwards, eventually emptying into the Mediterranean Sea.
- The river's geography was instrumental in shaping Egyptian civilization as it provided fertile land for agriculture, transportation, and protection against invasions.

2. Agricultural Benefits:
- The Nile River flooded annually, depositing nutrient-rich silt along its banks. This flooding created extremely fertile soil, known as "black land" or "Kemet," which was ideal for agriculture.
- The Egyptians developed a sophisticated irrigation system to control the river's flow, allowing them to cultivate crops year-round. They used canals, dikes, and reservoirs to distribute water across their fields.
- The primary crops grown by the ancient Egyptians included wheat, barley, flax, and various fruits and vegetables. The abundance of food from agriculture sustained the population and supported the growth of cities and trade.

3. Transportation and Trade:
- The Nile River served as a vital transportation route for the ancient Egyptians. The Egyptians used boats and ships to travel along the river for trade, communication, and exploration.
- The river's flow was predictable, making navigation relatively easy. Trade routes connected various cities along the Nile, allowing the exchange of goods and ideas.
- The availability of water transportation facilitated the growth of trade networks, both within Egypt and with neighboring civilizations, such as Nubia and the Mediterranean civilizations.

4. Cultural and Religious Significance:
- The Nile River held immense cultural and religious significance for the ancient Egyptians. They considered the river to be a divine gift and personified it as the god Hapi.
- The annual flooding of the Nile was believed to be the result of Hapi's tears of joy, bringing fertility and prosperity to the land.
- The Egyptians also associated the Nile with the afterlife. In their belief system, the river was a passageway to the realm of the dead. They buried their deceased on the west bank of the Nile, symbolizing the journey to the afterlife.

In conclusion, the Nile River was indeed the lifeline of Egyptian civilization. Its geographical features, agricultural benefits, transportation capabilities, and cultural significance made it the backbone of ancient Egyptian society. The river's influence permeated every aspect of Egyptian life, contributing to the prosperity and longevity of their civilization.