The correct option is D Amount of chlorophyll
Internal factors are genetic factors. These factors are responsible for the development of the genetic characteristics of a plant. The internal factors include number, size, age and orientation of leaves, mesophyll cells and chloroplasts, internal CO2 concentration and amount of chlorophyll. Chlorophyll is the primary pigment used during photosynthesis. When the amount of chlorophyll is more, the photosynthetic capacity of the plant will be more. External factors include the availability of sunlight, temperature, CO2 concentration in the surrounding environment and water.