Ocean trenches form over millions or billions of years. which statement accurately describes how ocean trenches form?

Regarding most of the narrator’s story, which word best describes the tone?

Most animal cell membranes have proteins that pump. ions out of the cell and potassium ions into this

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.