Final answer:
The Cambrian era is significant for the Cambrian Explosion, which was the rapid diversification of diverse animal life and the emergence of most major animal phyla.
Step-by-step explanation:
The start of the Cambrian era around 544 Mya is significant due to c) The explosion of diverse animal life, known as the Cambrian Explosion. During the Cambrian period, which spanned from 541 to 485 million years ago, there was the most rapid evolution of new animal phyla and a remarkable increase in animal diversity on Earth. This period saw the emergence of major groups of animals such as echinoderms, mollusks, worms, arthropods, and chordates, which include many of the ancestors of modern animals. The Cambrian explosion represents an unparalleled era of biological diversity and complexity blossoming in what seemed like a geological instant.