In an RF oscillator circuit designed for high stability, the positive feedback is drawn from two capacitors connected in series. These two capacitors would most likely be:

Silver mica capacitors are highly prized in radio frequency (RF) oscillator circuits because of their exceptional temperature stability and low tolerance. When an oscillator requires precise frequency control, the components in its tuned circuit must not change their values significantly as the equipment warms up. Other capacitor types listed are unsuitable for this specific high-stability application. Electrolytic capacitors have poor tolerances and high leakage, making them suitable only for DC filtering or low-frequency coupling. Mylar and standard ceramic capacitors often exhibit significant capacitance shifts with temperature changes, which would cause the oscillator's frequency to drift over time.