The correct option is B related genera
The taxonomic hierarchy includes categories, kingdom (highest taxonomic category), division, class, order, family, genus and species (lowest taxonomic category).
A class is a group of related orders. An order is a group of related families. The taxonomic category family is a group of related genera. Families are characterised on the basis of both vegetative and reproductive features of plant species. For eg: Solanum, Datura and Petunia are placed in the family Solanaceae due to certain common characters like persistent calyx, epipetalous condition and axile placentation.