How are till and outwash different me

If a robot fixed another robot is it a engineer or doctor?

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.

How are primary producers important to the alligator's energy supply