I believe the answer is b.
All invertibrates share one charistic in common, they have no backbone.
The correct answer is option D.
Invertebrates don’t have a common similarity in an anatomical structure that all have. They are different in their structure so they should not be grouped into one group.
All different groups of invertebrates have a different type of symmetry, composition, and anatomically different but there is not a common character except the fact that no one has vertebra.
Thus, the correct answer is option D.
In general vertebrates are organism that has backbone/spine or a vertebral column derived from notochord. While invertebrates are organism that do not have any backbone or vertebra column.
All classification terminologies categorize animals or plants on the basis of some common characteristics. However, in the case of this word invertebrate there is no categorization on the basis of common characteristics, it simply distinguish animals from each other on the basis of presence of backbone/spine/notochord.
Hence, option C is correct