Question

in parts of the united states midwest, you can find fossils of ancient sea creatures. some of these fossils could easily be mistaken for the remains of current day sea creatures, although they are only very distantly related.

the ancient fossils are a record of when shallow seas covered much of the united states. while the fossils are of organisms that are the precursors of many modern day organisms, changes in ocean geography and other factors eventually caused those older species to become ________
a adapted
b evolved
c extinct
d obsolete

Explanation:

The text states these ancient species are only distantly related to modern ones, and environmental changes led to their status. "Adapted" and "evolved" would mean they continued in a modified form, but the context notes they are precursors replaced by modern organisms. "Obsolete" refers to outdated objects, not species. "Extinct" means the species no longer exists, which fits the description of these older, replaced sea creatures.

Answer:

C. extinct