A difference in which of the following causes electron flow?

Voltage, also known as electromotive force or potential difference, is the electrical "pressure" that pushes electrons through a circuit. Without a difference in voltage between two points, there is no force to cause current to flow. Think of it like a plumbing system: a difference in water pressure causes water to flow from a high-pressure area to a low-pressure area. Capacitance and inductance are properties related to storing energy, and ampere-hours measure battery capacity, none of which act as the fundamental driving pressure for electrons.