Answer:
The correct answer will be- the similarity of morphological characters.
Step-by-step explanation:
The organism has been classified by many philosophers and scientists with the beginning of civilization like Aristotle and Carolus Linnaeus. But the most accepted classification used today was proposed by the Carolus Linnaeus in 1753 which he called the hierarchical system of classification also known as the classical system of classification.
This system was based on the similarity of morphological features between two organisms studied by the taxonomist which includes identification, nomenclature and classification.
Thus, the similarity of morphological characters is the correct answer.