Correct option is A
The correct answer is (a).
A monophyletic group, also known as a clade, consists of an organism and all of its descendants, including the common ancestor. It represents a single branch on the tree of life, and all members of the group share a unique set of characteristics inherited from their common ancestor. This is the defining feature of a monophyletic group in phylogenetic classification.
Incorrect options
Option (b) describes a polyphyletic group, which includes species from unrelated lineages and is not a natural grouping.
Option (c) refers to a group lacking a common ancestor, which is biologically invalid since all life shares ancestry. Groups without a common ancestor are often referred to as polyphyletic groups. These groups combine organisms that do not share an immediate or recent common ancestor.
Option (d) is incorrect as apomorphic characters (derived traits) are key for defining monophyletic groups. Groups always lacking them cannot be monophyletic.
