Explanation: Oscillator crystals, typically made of quartz, vibrate at a precise resonant frequency determined by their physical dimensions and material properties. These properties, especially the crystal's physical size and elastic constants, are sensitive to temperature changes. When the temperature fluctuates, the crystal slightly expands or contracts, altering its physical dimensions and affecting its vibrational characteristics. This directly causes the resonant frequency of the crystal to drift. To maintain a highly stable and constant frequency output from the oscillator, it is essential to keep the crystal at a consistent temperature. This prevents unwanted frequency variations, ensuring accuracy and reliability in radio communication and timing applications. Therefore, option B is correct. Option A is dismissive and provides no technical explanation. Option C is incorrect because a constant temperature *stabilizes* the frequency; it does not make frequency changes easier. Changing frequency usually requires a different crystal or more complex electronic methods.