Ganges river dolphin primarily live in freshwater.

Explanation:
The correct answer is option 'A' - Ganges river dolphins primarily live in freshwater. This statement is not correct because Ganges river dolphins are exclusively found in freshwater environments. Here's a detailed explanation:

Ganges River Dolphin:
The Ganges river dolphin, also known as the Gangetic dolphin or Susu, is a species of freshwater dolphin found in the Indian subcontinent. It is primarily found in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems in India, Bangladesh, and Nepal.

Habitat:
Ganges river dolphins have a preference for freshwater habitats and are generally found in rivers, lakes, and deep pools. They are well-suited to living in such habitats due to their physical adaptations, such as a long beak, flexible neck, and paddle-like flippers, which enable them to navigate through shallow and turbid waters.

Blindness and Hunting:
Ganges river dolphins have poor eyesight due to the murky nature of their habitat, and they primarily rely on echolocation to navigate and locate prey. They emit ultrasonic sounds, which bounce off objects in their environment and provide them with information about their surroundings. This ability to use echolocation helps them in hunting and navigating through the river system.

Size Difference:
Regarding the size difference between male and female Ganges river dolphins, it is incorrect to state that females are larger than males. In reality, there is no significant size difference between male and female Ganges river dolphins. Both genders generally reach a length of around 2 to 2.5 meters and weigh around 70 to 90 kilograms.

Only Species in India:
The Ganges river dolphin is indeed the only species of river dolphin found in India. It is listed as an endangered species and is protected under the Wildlife Protection Act of India. The population of Ganges river dolphins has been declining due to various factors such as habitat degradation, pollution, and accidental entanglement in fishing nets.

To summarize, option 'A' is not correct because Ganges river dolphins primarily live in freshwater, and they are exclusively found in freshwater environments. They have poor eyesight but use echolocation to navigate and locate prey. There is no significant size difference between male and female Ganges river dolphins. Finally, the Ganges river dolphin is the only species of river dolphin found in India.