The graph illustrates how a plant’s rate of photosynthesis varies as light intensity changes, at three different carbon dioxide concentrations. For each case, the temperature is $15\,^{\circ}\text{C}$. What is the limiting factor for the rate of photosynthesis at point X on the graph?
- Acarbon dioxide concentration
- Blight intensity
- Csurface area of the plant
- Dtemperature