Correct option is D
Explanation-
In red and brown algae, unlike green algae or higher plants Both the large (rbcL) and small (rbcS) subunits of Rubisco are encoded by the chloroplast genome. This is a unique feature of red algae (Rhodophyta) and some brown algae (Phaeophyceae), where the Rubisco enzyme is plastid-encoded in its entirety. In contrast, in higher plants and green algae, rbcL is encoded in the chloroplast, but rbcS is encoded in the nucleus.
Option a : Large subunit in chloroplast and small subunit in nucleus
This is true for green algae and higher plants, but not for red/brown algae. In green lineage, small subunit (rbcS) is nuclear-encoded and imported into the chloroplast. But in red and brown algae, both subunits are chloroplast-encoded — so this is incorrect in the context of the question.
Option b : Large subunit in nucleus and small subunit in chloroplast
The large subunit (rbcL) has never been encoded in the nucleus in any known photosynthetic eukaryote. This configuration is not observed in any algal group or plant.
Option c: Both large and small subunits in nucleus
Incorrect for all algae and plants. Rubisco large subunit is always encoded in the chloroplast genome across photosynthetic organisms. This scenario does not occur in red, brown, green algae, or plants.
Correct Option (Option d):
Both large and small subunits in chloroplast
