The correct answer is B: Provide the crystal with a specified parallel capacitance. To ensure a crystal oscillator operates on the frequency specified by the crystal manufacturer, you must provide the crystal with a specified parallel capacitance (load capacitance). The crystal's frequency is specified for a particular load capacitance. Crystal manufacturers specify the crystal frequency for a specific parallel load capacitance (typically 12 pF, 18 pF, or 30 pF). If the actual circuit capacitance doesn't match the specified load capacitance, the oscillator will operate at a slightly different frequency. To get the exact specified frequency, you must match the load capacitance. This is typically done with a trimmer capacitor or by designing the circuit to have the correct capacitance. The load capacitance affects the crystal's effective frequency through the crystal's motional parameters.