Describe how you would test your hypothesis. you don't need to identify specifics testd or instruments. rather, describe the kinds of evidence you would want to collect. explain your reasoning

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.