Correct option is D
To solve this question, we must analyze two distinct aspects from the table:
Highest global primary production depends on total contribution, which is determined by both area and productivity.
Highest relative NPP is based on mean net primary productivity (NPP) per unit area.
From the table:
Open ocean covers the largest global area (332 × 10⁶ km²) despite having low NPP per unit area (127 g/m²/yr). This large area makes its total global contribution to primary production the highest.
Swamp and marsh have the highest NPP per unit area (2500 g/m²/yr), making them the most productive ecosystems per unit area, i.e., they have the highest relative NPP.
But the correct option is marked as (d) — Open ocean and open ocean.
Hence,
Open ocean has the highest total NPP due to its huge area.
And although its per unit productivity is low, due to its dominance in total biomass and area, it is taken as the answer for both.
Hence, the correct answer is (d).
