The Average NPP Value for a Region of Ocean Is

Multiple Choice

The average NPP value for a region of ocean is 100 g C/m²/year.The average NPP for a tropical forest is 2,200 g C/m²/year.Yet oceans account for 24 percent of the world's total NPP, while tropical forests account for only 22 percent.What factor accounts for the discrepancy in average value and percentage of NPP for these two ecosystems?

A) Area covered by oceans is much greater than area covered by tropical forests.
B) Ocean NPP measurements are much less accurate than land measurements.
C) Ocean NPP is measured by depth instead of area, which dilutes the measurements.
D) Ocean NPP measurements have respiration subtracted; land measurements do not.
E) The two measurements were made at very different latitudes.