Some fossils, like this trilobite, are considered fossils. This type of fossil is used to help match the relative age of rock layers. In order to do this, the fossil must be found in many different places, during one time period, and have some unique characteristics.

The question is incomplete as it does not have the options which are:

A)C-14

B) index

C)trace

D)stratified

Option-B

Explanation:

An index fossil is defined as those fossils which are distributed over a large geographical area and appears for a shorter period of time.

They are very useful to the geologists as this fossil are useful in determining the relative age of the rocks. It also helps in the process of correlation of rocks.

In the given question, trilobite is considered an index fossil that appeared in the Cambrian period and got extinct by Permian period.

Thus, Option-B is the correct answer.

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