Step 1: Identify the length of the rivers.
The Ganga is the longest river in India, measuring approximately 2,525 kilometers.
The Yamuna, Godavari, and Brahmaputra are also important rivers, but they are shorter than the Ganga.
Step 2: Determine the geographical journey of the Ganga.
The Ganga originates from the Gangotri Glacier in the Himalayas and flows across northern India into the Bay of Bengal.
Step 3: Conclusion.
Since the Ganga is the longest river in India, the correct answer is option (B).