Geologic Time Scale.Scientists decide when an era begins<span> and </span>ends<span>, due </span>to<span> mass extinction. ...</span>Scientists determine<span> when drastic changes </span>are<span> made by the fossil record, which shows earths past organisms that have become extinct.</span>
Hope this helps! This is what I found when googling it!
Answer:
Have hard parts
Were generally large
Lived in a narrow range of geographical area
Are extinct
Explanation:
C is your answer :)
Hope it helps!
