Natural system of classification is given by

Explanation:
Bentham and Hooker - Proposed the natural system of classification.
Carolus Linnaeus- The father of classification, He classified all the living organisms under two large kingdoms, i.e., kingdom plantae and kingdom animalia.
Charles Darwin- Proposed the theory of Natural selection.
Engler and Prantl- Proposed system of classification based on the sequence of evolution  between various groups of plants.

Final Answer:
Hence option A: Bentham and Hooker is the correct answer. Natural system of classification is given by Bentham and Hooker.