The correct answer is option 'C', Amu Darya.

Explanation:
The Oxus River, also known as Amu Darya, is one of the major rivers in Central Asia. It has been an important river throughout history, and its ancient name is Oxus.

The Oxus River is formed by the confluence of the Vakhsh and Panj rivers, which originate in the Pamir Mountains in Tajikistan. It flows through Tajikistan, Afghanistan, and Turkmenistan before emptying into the Aral Sea.

Historically, the Oxus River played a significant role in the region's trade and transportation routes. It connected the ancient civilizations of Central Asia, such as Bactria and Sogdiana, with other parts of the world. The river valley was home to many ancient cities and settlements that thrived due to the fertile land and access to water for irrigation.

During the time of Alexander the Great, the Oxus River marked the easternmost boundary of his empire. It served as a natural barrier between the Greek territories and the vast Central Asian steppes. Alexander attempted to cross the river and explore the lands beyond, but his troops were reluctant, and he was forced to turn back.

In later centuries, the region surrounding the Oxus River came under the control of various empires and kingdoms, including the Persian Empire, the Arab caliphates, and the Mongol Empire. The river continued to be an important trade route, facilitating the exchange of goods and ideas between different cultures.

Today, the Amu Darya remains a vital water source for the countries it flows through. It supports agriculture and provides hydroelectric power. However, the river's flow has been significantly reduced due to irrigation projects and the diversion of water for agricultural purposes.

In summary, the ancient name of the Oxus River is Amu Darya. It has played a crucial role in the history and development of Central Asia, serving as a trade route and a source of water for agriculture.