Question

question 2 of 10
what is an index fossil?
a. a fossil found in rocks from one time period
b. a fossil that formed 300 million years ago
c. a fossil that contains rocks and minerals
d. a fossil that has vestigial structures

Explanation:

Index fossils are fossils that are used to define and identify geologic periods. They are typically widespread, abundant, and existed for a relatively short period of time. Option B correctly describes an index fossil as a fossil that formed during a specific time period (in this case, 300 million years ago), which is a key characteristic of index fossils. Option A is too general as many fossils are found in rocks. Option C is incorrect as it doesn't capture the essence of being used for dating. Option D is also incorrect as it describes a different characteristic of fossils.

Answer:

B. A fossil that formed 300 million years ago