The suffix '$idae$' refers to:

$A$ group of families constitutes a/an ......... .

How many of the following statements are correct?
$(A)$ Each taxonomic category is a unit of classification.
$(B)$ Taxonomic groups are distinct biological entities.
$(C)$ Genera are aggregates of closely related families.
$(D)$ Both vegetative and reproductive characters are used to characterise the families.

Which of the following taxonomic categories contains the least number of similarities?

The book "Genera Plantarum", which contains the classification of seed plants, was written by .......

What is a species?