To compare the relative ages of fossils, scientists sometimes use an easily recognized

species called a (an):

a. index fossil

b. sedimentary fossil

c. carbon fossil

d. radioactive fossil

The fossil is A) Index fossil.

Explanation:

Index fossils refer to the type of fossil which is used to characterize and distinguish geologic periods. Due to this function of index fossil, they are also called as guide fossil or indicator fossil. These fossils must have a short vertical range, wide geographic circulation, and quick developmental patterns.

Another term, Zone fossil is utilized when the fossil have every one of the characters expressed above with the exception of wide topographical dispersion, they are restricted to a zone and can't be utilized for relationships of stratas.