Refer to the figure.
The figure shows the CO₂ uptake by various leaf layers in a tropical forest. Leaf layer 1, at the top of the canopy, has the highest net rates of photosynthesis and layer 15 has the lowest net rates.
-What principles of production explain this pattern?

A) Leaves at the top of the canopy are larger than leaves at the bottom of the forest.
B) Gross carbon uptake is highest in top leaves relative to metabolic losses because upper leaves are in full sunlight.
C) Respiratory costs are increased in upper leaves relative to lower leaves because of the cost of transporting water and nutrients from roots to the top of the canopy.
D) The most productive plants in the forest reach the canopy first and maintain their productive advantage.