What two elements have the same number of energy level (shells)?

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

After a group of researchers conducts a new experiment that has never been conducted before, what is the best way for other scientists to make sure that the data is real

How can scientists use the fossil record to find evidence of relationships between different species?