Which statement best describes the role of phosphorus in the body? a. used to build proteins b. converts food to energy c. used to build genes d. weakens strong bones and teeth

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.