Which branch of science deals with the identification and relationships of organisms?

Each category in the classification of organisms forms a .....

In the scientific name $Homo$ $sapiens$ $sapiens$,what does '$c$' indicate?
$\frac{Homo}{a}$ $\frac{sapiens}{b}$ $\frac{sapiens}{c}$

Which of the following is not a taxon but a category?

Which of the following represents the correct sequence in taxonomic hierarchy?

$X$ being a higher category is the assemblage of families which exhibit a few $Y$ characters. The $Z$ characters are less in number as compared to different genera included in a family. Identify $X$, $Y$, and $Z$.