Explanation: Crystal oscillators utilize the piezoelectric effect, where a quartz crystal vibrates mechanically at a precise frequency, translating into an equivalent electrical resonance. 1. **Very high Q:** Crystals exhibit a Quality factor (Q) orders of magnitude higher than typical LC (inductor-capacitor) tuned circuits. This is because mechanical resonators have significantly lower energy losses than electrical components, resulting in an exceptionally sharp and well-defined resonant peak. 2. **Compact size:** For a given radio frequency, the physical dimensions of a quartz crystal are much smaller than the bulky coils and capacitors required to form an equivalent resonant LC tank circuit. 3. **Excellent frequency stability:** This is a primary advantage. The resonant frequency of a crystal is determined by its highly stable physical dimensions and material properties, making it much less susceptible to temperature changes, voltage variations, and aging effects compared to discrete L and C components. The extremely high Q factor also contributes directly to this superior stability, ensuring the oscillator stays precisely on frequency. Since all three statements are significant advantages of crystal control over tuned circuit oscillators, **D) All of the above** is the correct answer.