Why are liver cells a example of slow rate division

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

One important development during the 3rd trimester that will insulate the infant against changes in temperature is a. the deposition of fat under the skin b. the closing of the septum between c. the atria of the heart d. the beginnings of lung functioning e. the beginnings of light and sound sensing

The largest unit within which gene flow can readily occur is a