1 Which of the following statements about cellular respiration is true?
A Animals do not carry out cellular respiration.
B Cellular respiration is the process by which some living things take energy from the sun to make food.
C Oxygen is a product of cellular respiration.
D Oxygen is a reactant of cellular respiration.

your answer is "the 1950's"

the answer is d. chordata

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.