Which of the following conditions would most likely lead to the failure of a resistor due to overheating?

Correct Answer: Option A — Resistor wattage rating one half that required for the circuit.

Resistors must be sized to dissipate heat generated by current flow (I²R). Selecting a wattage rating half of the circuit requirement causes the component to operate significantly above its thermal capacity. This leads to rapid oxidation, resistance drift, and eventual catastrophic failure of the resistive element.