Whales and dolphins like fishes live in water. But they do not have gills. How do they breathe?

The correct option is C

Explanation of the correct answer:

1. ​Whales are mammals who breathe air into their lungs.
2. Blowholes are a whale's nostrils and are located on the top or back of the whale's head.
3. Blowholes are covered by muscular flaps that keep water from entering them when the whale is under water.

Explanation of the incorrect answers:

Option A:

1. All multicellular complex living organisms require oxygen for living, weather aquatic or terrestrial.
2. Hence, dolphins and blue whales require oxygen for respiration as they do aerobic cellular respiration.

Option B:

1. Breathing through moist skin is possible only in simple organisms like earthworm.
2. In complex and bigger organisms the oxygen will not reach the deeper tissues of the organisms by simple diffusion.
3. Hence, it is not possible in dolphins and whales.

Option D:

1. Spiracles as the openings for breathing in arthropod, for example cockroach.
2. They are the part of the tracheal system for respiration which is absent in mammals like dolphins and blue whales.

Final answer: Whales and dolphins like fishes live in water. But they do not have gills. They breathe through blowholes.