DNA makes a copy of itself before division A - mitosis
B - meiosis
C - both

(if someone could answer this for me it would help so much)

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.