What is a factor that can influence the rate of a nuclear decay reaction?

the pressure applied to the reactant over time
the stability of the radioactive element
the amount of the reactant broken down over time
the temperature applied to the reactant over time

Before it was launched, a helium-filled balloon had a pressure of 201 kpa at a temperature of 27°c. at an altitude of 15,000 m, the pressure had decreased to 2.5 kpa and the temperature had dropped to -14 °c. the volume of the balloon increased to 59.3 m3. what is the original volume of the balloon? 13 m3 0.85 m3 0.077 m3 1.17 m3