Question

Why are index fossils good indicators of geologic time?

A. They are rare.

B. They lived during a short period of geologic time.

C. They lived during a long period of geologic time,

D. They lived with humans,​

Answer 1

B. They lived during a short period of geologic time.

Step-by-step explanation:

Index fossils are used to define and identify geologic periods. Index fossils must have a short vertical range, wide geographic distribution, and rapid evolutionary trends.

Answer 2

the answer is B

Step-by-step explanation: