Step 1: Classification systems are usually grouped as artificial, natural, or phylogenetic. Engler and Prantl, Hutchinson and Bessey are all considered phylogenetic since they try to show evolutionary lines of descent.
Bentham and Hooker's system, based on overall resemblance in floral and vegetative characters without assuming an evolutionary sequence, stands as the natural system among these four.
Final answer: Bentham and Hooker's system.