Final answer:
Corals first appeared during the Silurian Period, between 440 and 410 million years ago, preceding the Triassic, Jurassic, Cretaceous, and Pleistocene times.
Step-by-step explanation:
Corals first appeared in Australia during the Silurian Period, which occurred between 440 and 410 million years ago. This is significantly earlier than any of the periods listed in the multiple-choice question. During the Silurian Period, corals began to emerge in oceans and alongside this, the evolution of fish continued, while vascular plants began to show up on land.
The Triassic Period (245–200 million years ago) marked significant biological developments, including the rise of dinosaurs and the separation of the supercontinent Pangaea, but corals had already been part of Earth's marine ecosystems well before this time. The first coral reefs may have developed during the Devonian period when coral diversity greatly increased, followed by their peak and later extinction at the end of the Permian period.