The Yamuna river is one of the major rivers in India and is considered a tributary of the Ganga river. It originates from the Yamunotri Glacier in the lower Himalayas and flows through the northern states of Uttarakhand, Himachal Pradesh, Haryana, Delhi, and Uttar Pradesh before joining the Ganga river at the Triveni Sangam in Allahabad, Uttar Pradesh.

The Yamuna river flows parallel to the Ganga river, making option B, Ganga, the correct answer to the question.

The Yamuna river and the Ganga river are two of the most sacred rivers in India and are considered lifelines for millions of people. Let's understand why the Yamuna river flows parallel to the Ganga river.

The Ganga-Yamuna Doab:
The Ganga-Yamuna Doab is a fertile region located between the Ganga and Yamuna rivers. It is formed by the alluvial deposits brought by these rivers over thousands of years. The Doab region is known for its rich soil and is one of the most densely populated regions in India.

The Yamuna river, in its course, runs almost parallel to the Ganga river in the Ganga-Yamuna Doab. This parallel flow is due to the geographical positioning of the rivers. The Yamuna river flows to the east of the Ganga river, maintaining a parallel course for a significant distance.

Significance of the Parallel Flow:
The parallel flow of the Yamuna and Ganga rivers has several implications:

1. Irrigation: The parallel flow of these rivers in the Ganga-Yamuna Doab provides ample opportunities for irrigation in the region. Farmers can harness the water resources of both rivers for agricultural purposes, enhancing productivity.

2. Connectivity: The parallel flow of the Yamuna and Ganga rivers also facilitates transportation and connectivity in the region. Numerous cities, towns, and villages are located along the banks of these rivers, and the parallel flow allows for easy movement of people and goods.

3. Religious Significance: The Yamuna river is considered highly sacred in Hinduism, and its parallel flow with the Ganga river adds to its religious significance. Many religious sites and pilgrimage centers are situated along the banks of these rivers, attracting millions of devotees every year.

In conclusion, the Yamuna river flows parallel to the Ganga river in the Ganga-Yamuna Doab region. This parallel flow has several implications, including irrigation, connectivity, and religious significance.