In addition to possibly being the cause of bald eagle deaths, hydrilla can cause many other problems. all but one may be an ecological issue with the invasion of hydrilla in georgia water.

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.