Assertion: The external factors that affected photosynthesis are number, size age and orientation of leaves, mesophyll cells and chloroplasts and the amount of chlorophyll.
Reason: The internal factors that affect photosynthesis are availability of sunlight, temperature `CO_(2)` concentration and water.

Answer

D

Explanation

Photosynthesis is under the influence of several factors both internal (plant) and external. The plant factors include the number, size age and orientation of leaves, mesophyll cells and chlorolasts, internal `CO_(2)` concentration and the amount of chlorophyll. the plant or internal factors are dependent on the genetic predisposition and the growth of the plant. the external factors inclue the availability of sunlight, temperature `CO_(2)` concentration and water. During phosotsynthesis, all these factors simultaneously affect its rate.