Answer:
B ratio of neutrons to protons
Step-by-step explanation:
The stability of an atom is determined by the ratio of neutrons to protons in the nucleus of an atom. The lager the ratio of neutrons to proton the lesser is the stability of the nucleus. The n to p ratio of higher atomic number that exist in a number of isotopic form is higher and their stability is low. The uranium 238 breaks down to lead 206.