How are organisms in the domains bacteria and archaea similar
a- they contain protists
b- they contain nuclei
c- they are multicellular
d- they prokaryotes

The correct option is D. Both bacteria and archaea are prokaryotes.

Explanation:

Prokaryotes are organisms made up of a single cell and do not possess any of the organelles which are bounded by a membrane. Prokaryotes can be classified into two categories: archaea and bacteria. Hence, option D is correct.

Other options are false because

Option A: Bacteria and archaea are not protists.

Option B: They do not contain a nucleus and their genetic material is present in the form of the nucleoid.

Option C: They are not multicellular.

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.