Answer:
Explanation:............................................
The subordinate clause here is A, "as the layers of ash slowly compressed". Subordinate means that it cannot exist on its own, it has to be a part of the main, independent clause.
The answer is Historical works that are so important they change the way we see the world.
Explanation:
Seminal works, sometimes called pivotal or landmark studies, are articles that initially presented an idea of great importance or influence within a particular discipline.
Examples are comma, colon, semi-colon, Dash, parentheses,