A sample of phosphorus was isolated and analyzed to determine the percent abundance of each isotope The results are recorded in the table below Isotope Phosphorus 29 Phosphorus 31 Phosphorus 32 Mass amu 29 31 32 Percent Abundance 5 71 24 Based on the data which statement gives the best reasoning for the average atomic mass for the isotopes of 31 14 amu Phosphours 31 makes up the majority of the sample so the average atomic mass should be close to 31 It is the sum of neutrons and electrons in the isotopes found in a sample It is the mean of all of the different isotopes of phosphorus present in the sample It is the total number of neutrons protons and electrons in the isotopes found in a sample of phosphorus