D. Modern classification differs from the systems used by Aristotle and Linnaeus in that it looks at similarities and differences in DNA found in the cells of organisms. Aristotle and Linnaeus used primarily morphological characteristics (such as physical appearance) to classify organisms, whereas modern classification takes into account a wide range of information, including DNA sequences, embryonic development, and ecological relationships. Additionally, modern classification may use microscopes to examine tiny structures that organisms may have, but this is not a defining characteristic of modern classification. Similarly, while modern classification may look at fossils to understand the evolutionary relationships between organisms, this is not a defining characteristic of modern classification.