In your opinion which type of source will be most common in the future choose the following explain why 1) coal 2) oil 3) natural gas

In my opinion, natural gas is a source that will be most common in the future. Considering that natural gas is a fossil fuel that is used as a source of energy for heating, cooking, and electricity generation. It is also used in stoves, ovens, clothes dryers, lighting fixtures and other appliances that are used and needed in everyday life. Imagine a life without natural gas. We wouldn't be able to heat our homes, cook our food, etc.  

the answer for apex is "1 and 6"

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.