Which process is a "build up" process? which process is a "break down" process? photosynthesis occurs in what organelle? cellular respiration occurs in what organelle?

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.