The correct answer is option 'C' - Ganga.

The Ganga River, also known as the Ganges, is home to freshwater dolphins. Here is an explanation of why the Ganga River is the home for freshwater dolphins:

1. Habitat:
- The Ganga River provides an ideal habitat for freshwater dolphins due to its large size, depth, and flow.
- Dolphins prefer deep and slow-moving waters, which can be found in some stretches of the Ganga River.

2. Ganges River Dolphin:
- The Ganges River Dolphin, also known as the South Asian River Dolphin or Susu, is a freshwater dolphin species found in the Ganga River.
- It is one of the few remaining freshwater dolphin species in the world and is considered an indicator of the river's health.

3. Adaptations:
- Ganges River Dolphins have adapted to their riverine environment over time.
- They have long and slender bodies, making it easier for them to navigate through the water.
- They also have a long snout, which helps them in finding food by sensing vibrations in the water.
- Their eyesight is weak due to the murky waters of the river, so they rely on echolocation to locate prey and navigate.

4. Endangered Species:
- Ganges River Dolphins are listed as an endangered species due to various factors such as pollution, habitat degradation, and accidental entanglement in fishing nets.
- Conservation efforts are being made to protect and preserve these dolphins and their habitat.

In conclusion, the Ganga River is home to freshwater dolphins, specifically the Ganges River Dolphin. This species has adapted to the river's unique ecosystem and is considered an indicator of the river's health. However, these dolphins are endangered, and conservation efforts are necessary to ensure their survival.