when medical professionals encounter a disease, they often to make an ethical decision about the prescription of an antibiotic. explain how the information in the paragraph supports the use of restraint when prescribing antibiotics.

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.