The broadest category of organism in biological taxonomy is

A

Phylum

B

Class

C

Kingdom

D

Family

The broadest category of the organism in biological taxonomy is a kingdom. 

Each unit or category of classification is termed as a taxon. It represents a rank. For example, the basic level of classification is species, followed by genus, family, order, class, phylum or division, in ascending order. The highest level of classification is known as the kingdom.