Based on the information in the graph, which atom listed below is the most stable?

a. helium-4 (he-4)
b. iron-56 (fe-56)
c. uranium-238 (u-238)
d. hydrogen-3 (h-3)

Iron-56 has the greatest binding energy per nucleon while Hydrogen-3 has the lowest based on the information in the graph of average binding energy per nucleon against number of nucleons in nucleus. We know that the the greater the amount of binding energy per nucleon the greater the nuclear stability is, thus Iron-56 is the most stable atom among Helium-4, Uranium-238 and Hydrogen-3.