The correct answer is red algae.

Red algae is just named ‘red’, because of the pigment it contains - ‘phycoerythrin’. This phycobilin/phycoerythrin can absorb the blue light and use it for photosynthesis, thus using the little solar energy that reached the deepest part of the ocean for manufacturing food. Hence, the red algae is able to survive the deepest quarters of the oceans while the others can’t.

Correct

Correct

red algae

For sustaining life in the deepest waters, energy is necessary. Algae synthesize their food by using solar energy. At the bottom of deep water bodies, only high energy components of the solar spectrum are able to reach. 

The blue and green light components have short wavelengths and hence high energy. So, blue-green light reaches the bottom. This blue-green light is absorbed by the pigment phycoerythrin which is present in red algae. Hence, red algae is likely to be found in the deepest waters.

Red algea

Red algae

Red algae