Respuesta :
Index fossils were fossils that are routinely used to identify a geologic era of time, and they are also widely distributed and have quick evolutionary patterns.
- It will be any animal or vegetation left in the Earth's geologic record that is unique to a particular period of geological timescales or environment.
- The index fossil has to be distinct or easily recognizable, plentiful, get wide geographic distribution, and also have a short temporal span.
Therefore, the answer is "Option 3".
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