Plants Lose Several Hundred H₂O Molecules for Each CO₂ That

Multiple Choice

Plants lose several hundred H₂O molecules for each CO₂ that is fixed by photosynthesis because:

A) the concentration gradient is many times larger for H₂O than for CO₂.
B) H₂O molecules are lighter than CO₂ molecules and thus diffuse faster.
C) H₂O molecules are consumed during photosynthesis.
D) the evaporation of so many H₂O molecules is necessary to keep photosynthesis at its optimum temperature.