Humans can maintain a stable internal temperature by?

a. sweating when the body gets too hot.

b. releasing insulin when there is a high amount of sugar in the blood.

c. getting a fever when an infection comes into the body.

d. squinting to limit the amount of light entering the eye.

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.