The correct answer should be A. subdivisions
Usually, they are split into numbers for the highest and broadest rank, then capital letters for subdivisions, and then lower case letters for the lowest place in the hierarchy.
I would think the answer is “C”, I don’t see a problem-solution or a cause & effect in the passage, and there is no chronological order of anything. So my answer would be “Fact by Fact”
This one: "Lee noticed a problem and alerts a teacher".
The second verb should not have been changed to present tense.
You should change the verb alert to past tense: "Lee noticed a problem and alerted a teacher".
Paleozoic Era, also spelled Palaeozoic, major interval of geologic time that began 541 million years ago with the Cambrian explosion, an extraordinary diversification of marine animals, and ended about 252 million years ago with the end-Permian extinction, the greatest extinction event in Earth history. The major divisions of the Paleozoic Era, from oldest to youngest, are the Cambrian (541 million to 485.4 million years ago), Ordovician (485.4 million to 443.8 million years ago), Silurian (443.8 million to 419.2 million years ago), Devonian (419.2 million to 358.9 million years ago), Carboniferous (358.9 million to 298.9 million years ago), and Permian (298.9 million to 252.2 million years ago) periods. The Paleozoic takes its name from the Greek word for ancient life.
