Hey guys...clear the one thing as per option A chlorophyll a is same but what about the pigments???xanthophylls is present in brown algae and phycoerythrin is present in red algae how it will become similar??but in option C group keps and diatoms accessory pigments are same...the pigments are fucoxanthin and brown pigments/brown algae are present in same of kelps and diatoms.. so the option C is correct answer...

Similarity in Pigment Composition of Red Algae and Brown Algae
• Both Red algae and Brown algae have a similar pigment composition, containing chlorophyll a and c, as well as fucoxanthin.
• Fucoxanthin is a unique accessory pigment that gives these algae their characteristic brownish color.
• This pigment composition helps them to efficiently absorb light in the deeper waters where they are commonly found.

Explanation:
Red algae (Rhodophyta) and Brown algae (Phaeophyta) belong to different algal groups but share similarities in their pigment composition. Both groups contain chlorophyll a and c, which are the primary photosynthetic pigments responsible for capturing light energy. In addition to chlorophyll, they both contain fucoxanthin, a brown-colored pigment that masks the green color of chlorophyll and gives these algae their characteristic hues.
Fucoxanthin is an accessory pigment that plays a crucial role in photosynthesis by absorbing light energy that chlorophyll alone cannot capture effectively. This pigment allows red and brown algae to thrive in deeper waters where light penetration is limited, making them well-adapted to various marine environments.
Overall, the similarities in pigment composition between red algae and brown algae highlight their evolutionary adaptations to their respective habitats and contribute to their ecological success as important primary producers in marine ecosystems.