The correct option is B It is a natural systems of classification of all groups of plants.
Bentham and Hooker gave the natural system of classification in which the seeded plants are divided into dicotyledons, gymnosperms and monocotyledons. The dicotyledons are divided into Polypetalae, Gamopetalous, and Mmonochlamydeae. This classes where further divided into cohorts. The classification is based on the natural observation of species. The placement of Gymnospermae between Dicotyledonae and Monocotyledones was considered as a demerit of this classification. Thus, the correct answer is option B.