In the given diagram,what do the parts labeled $P$ and $Q$ represent respectively?

What is the full form of $ICBN$?

What is the science of classifying all living organisms into different taxa based on their characteristics called?

As we go higher from species to kingdom,the number of common characters?

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.

The correct sequence of taxonomic categories is: