Which characteristic defines all dichotomous keys?

Each key is a series of statements.
Each key is organized as a table.
Each key is organized as a flowchart.
Each key is a mathematical formula.

c. Each key is organized as a flowchart.

Explanation:

A dichotomous key is a device that enables users to recognise natural world objects, such as wildflowers, trees, reptiles, mammals, fish and rocks. it used for the Identification whereby groups of species are frequently divided into two categories with increasing sequential division, more information on the basic characteristics of a particular organism is released.

Dichotomous keys are represented in two ways including either as descriptive representation in which a series of paired statements arraged in a numbered sequence or as a branching flowchart (diagrammatic representation) .

Hence, the correct option is c.