2 Points
What is an index fossil?
O
A. A fossil that contains rocks and minerals
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B. A fossil found in rocks from one time period
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C. A fossil that has vestigial structures
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D. A fossil that formed 300 million years ago

B, A fossil found in rocks from one time period

Explanation:

Fossils are used to determine the ages of rock layers. Index fossils are the most useful for this. Index fossils are of organisms that lived over a wide area. They lived for a fairly short period of time. An index fossil allows a scientist to determine the age of the rock it is in. Hope that this helps you :)

it always confuses me when i see it

the water is warmed up by the sun and then it evaporates into the atmosphere. the sunlight warms the water by its heat. water is then cooled down and condensation takes place. the water then finally returns back to the earth by the process of precipitation in the form of rain or ice.

explanation: