Final answer:
Brain heart infusion broth is considered a complex medium since it contains undefined and variable components, aside from the chemically defined elements like certain minerals and trace elements. It primarily serves as a complex medium due to the presence of extracts and digests of yeasts, meat, or plants.
Step-by-step explanation:
In brain heart infusion broth (a complex, non synthetic media), none of the ingredients can be chemically defined except for certain minerals and trace elements. These elements may include Cu, Zn, Co, Mn, and others, which are known and can be precisely measured in the media. The broth also contains complex extracts like those derived from animal brains and hearts, which makes it a complex medium rather than a chemically defined one.
The correct statement regarding brain heart infusion broth is that it includes elements from all the options provided (a selective medium, a differential medium, and a complex medium), but it is primarily known as a complex medium, because it contains ingredients with undefined quantities and undetermined chemical compositions. However, chemically defined media like EZ medium have known concentrations of all their components, unlike brain heart infusion broth.