Answer:
Paleozoic
Explanation:
The Paleozoic Era is a geologic era that lasted from 541 to 251.902 million years ago. This is divided into six geologic periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The swamps that were turned into coal over time grew during the Carboniferous period, which expands from 358.9 million years ago to 298.9 million years ago. The period is well-known because many coal beds were formed during that time period. During the Carboniferous, terrestrial animals were well-established. It ended with a minor extinction event known as the Carboniferous rainforest collapse.
I assume that the question refers to the political affiliation of the Islands (They are Islands in the Mariana Trench, in the Pacific Ocean, south of Japan) - they are politically linked to the US - the correct answer is a). For example the Mariana islands have a commonwealth status within the US.
