Answer:
Option-A
Explanation:
Index fossils are the fossils that are used to determine and identify the geological time period. The index fossils are thus also known as the guide fossils or type fossils or indicator fossils.
The index fossils are found in the wide geographical distribution in the rocks evolutionary trends. The index fossils are usually found in the ocean and rarely in the terrestrial landforms.
Thus, Option-A is correct.
