The layer of clay that marks the boundary between the mesozoic and cenozoic is rich in what element?
a. carbon b. oxygen c. iridium d. iron e. sodium

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