Answer:
Letter H is a(n) intrusion.
Which of these is youngest? Letter G
Which of these was eroded? Letter C
Which happened first? Letter F was deposited.
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I just did the review for it and these are the answers. The person above is correct, but if you want what the answer is in wording and not numbers, then this answer would be suited for you.
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Have a great day and God bless! :)