Assuming the stomata are open to the same degree, the rate of transpiration should decline on a rainy day compared with a sunny day, because the relative size of the H2O concentration gradient from the inside to the outside of the leaf would decrease.
Option: A
Step-by-step explanation:
During the dry season transpiration levels were stronger than during the wet season, due largely to increased demand for evaporation and the depletion of groundwater supplies by trees. Transpiration levels showed a strong hysteresis in relation to the deficit in vapor pressure, which was more pronounced in the dry season than in the wet. This consequence may be due to low hydraulic conductivity in the soil, or the use of accumulated stem water, or both.