The answer would be...
2) the temperature is too cold.
Answer: They existed for a short span of time.
Explanation:
Index fossils are also referred to as the indicator fossils and they are simply used to define the faunal stages.
Some of the characteristics possessed by the index fossils include:
• geographic distribution that's wide
• short vertical range
• rapid evolutionary trends.
The answer is A. Sorry if i'm wrong.
