Option 1: Blue-finned Mahseer is indeed found in the Cauvery River, but the Irrawaddy Dolphin is not found in the Chambal River. So this option is partially correct and partially incorrect.

Option 2: The Irrawaddy Dolphin is not found in the Chambal River, but the Rusty-spotted Cat is found in the Eastern Ghats. So this option is also partially correct.

Option 3: Blue-finned Mahseer is found in the Cauvery River and the Rusty-spotted Cat is found in the Eastern Ghats. This option has both species correctly matched with their natural habitats which makes it the correct choice.

Option 4: Since the Irrawaddy Dolphin does not inhabit the Chambal River, this option is incorrect.

The key error in the incorrect options is mistakenly placing the Irrawaddy Dolphin in the Chambal River, while it is actually found in areas such as the Bay of Bengal and Southeast Asia.