Which piece of information obtained directly from a mass spectrum is essential for calculating the average atomic mass of a sample so that it can be compared with periodic-table values?
a) The mass-to-charge ratio of the most abundant isotope only
b) The relative abundance of each isotope and its mass-to-charge ratio
c) The first-ionization energy of each isotope and its half-life
d) The accelerating voltage applied to the ions and the length of the flight tube