You are going to mix a gallon bucket of window cleaner. the instructions direct you to mix 1 part cleaner to 3 parts water. how much cleaning solution will you need to use?

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.