The correct answer is C: Through a capacitive divider. In a Colpitts oscillator, positive feedback is supplied through a capacitive divider. The Colpitts oscillator uses two capacitors in series to form a voltage divider, with the junction between them connected to provide feedback. The capacitive divider creates a phase shift and provides the feedback necessary for oscillation. One capacitor is typically in the feedback path, and the other is in parallel with the inductor, forming the tank circuit. The ratio of the capacitors determines the feedback amount and helps set the oscillation frequency. The Colpitts oscillator is popular because it doesn't require a tapped inductor (unlike the Hartley), making it easier to build and tune. The capacitive divider is the key distinguishing feature of the Colpitts oscillator.