Incorrect Pairing: Whale - River

The incorrect pairing among the given options is the pairing of a whale with a river. Let's understand why this pairing is incorrect and why the other pairings are correct.

Camel - Desert:
Camels are often associated with deserts because they are well-adapted to survive in dry and arid environments. They have physiological adaptations that allow them to conserve water and withstand extreme heat, making them suitable for the desert habitat. Therefore, the pairing of a camel with a desert is correct.

Germs - Air:
Germs, also known as microorganisms or bacteria, can be found in various environments, including the air. They are microscopic organisms that are present in the environment and can be transmitted through the air. Therefore, the pairing of germs with air is correct.

Polar Bear - Snow:
Polar bears are well-known inhabitants of the Arctic region, where they live in cold and snowy environments. Their white fur helps them blend in with the snowy landscape, and they are adapted to survive in the extreme cold. Therefore, the pairing of a polar bear with snow is correct.

Whale - River:
Whales, which are large marine mammals, are not typically found in rivers. Whales are adapted to live in saltwater environments, such as oceans and seas. They have streamlined bodies and fins that help them navigate through the water. While some species of whales may enter rivers temporarily for various reasons, such occurrences are rare and not typical of their natural habitat. Therefore, the pairing of a whale with a river is incorrect.

In conclusion, the correct pairings among the options are camel - desert, germs - air, and polar bear - snow. The incorrect pairing is whale - river because whales are not commonly found in rivers.