Answer:
A. Index fossils are useful tools for geologists because they can provide information about the relative age of rocks and help to correlate rock formations across different locations. By identifying and dating the age of index fossils found in a particular rock layer, geologists can determine the approximate age of the rock layer and its correlation with other rock layers in the region.
B. Three characteristics of a good index fossil are:
Widespread distribution: A good index fossil should have a wide geographic distribution, which means that it should be found in multiple locations around the world. This helps to establish a correlation between different rock layers that contain the same index fossil.
Limited time range: A good index fossil should have a limited time range, meaning that it should have existed for a relatively short period. This allows geologists to narrow down the age range of the rock layer containing the fossil.
Easily recognizable: A good index fossil should be easily recognizable, even in small or fragmented pieces. This allows geologists to quickly identify and date the fossil, even if only a small portion of it is present in the rock layer.
Overall, a good index fossil should be distinctive, easily recognizable, have a wide distribution, and a limited time range, all of which can provide useful information for geologists studying the history of the Earth.
Step-by-step explanation: