Answer:
Cambrian explosion
Step-by-step explanation:
Cambrian explosion is a geological event that happened during the Cambrian age (541 million years ago). In this period, most of the animal phyla (including marine) appeared and their geological record is preserved in the form of fossils. The period lasted for 13-25 million years. Before this period, the organisms were very simple. They were mostly unicellular in nature and were living in the form of colonies.
The remaining three options are incorrect. They are tectonic events that reflect movement of continents in different geological times. None of them resulted in the diversification of (marine) animal phyla.