Index fossils found in rocks can be used to help determine the rock's age, because index fossils are fossils of species that .
a changed their diets
b hid in marine sediments
c migrated to different environments
d quickly became extinct

Almost 98% of earthquakes occur at the boundary of a tectonic plates when they slide against one another. despite this, indiana still has seismic zones that experience increased seismic activity. this is particularly heavy in the wabash valley fault zone in the southwest corner of the state. how do you explain how seismic activity is felt in this area?