B. False. It was the French soil.
Answer:
a. They must be present in a large geographic area.
Explanation:
Index fossils can be used to determine the age of a rock strata with great precision, but they must be scattered over a large geographic area to be able to be used reliable for this type of measurement. Index fossils typically indicate a certain type of paleoenvironment belonging to a very specific prehistoric period and their formation coincides with the age of the rock layer.
