The problem with the older classification system is that classifying according to DNA similarities can be misleading. Thus, the correct option is D.
Carolus Linnaeus in the 18th century proposed the traditional system of classification of organisms based on their structure and characteristics. This we name a taxonomic nomenclature.
Classifying organisms on the basis of their overall similarity or DNA similarity can be misleading. For example, dolphins and whales, humans and chimpanzees, etc.
Therefore, the correct option for this question is D.
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