Explanation: A silicon crystal, when used in mixer and detector stages, acts as a semiconductor diode. Diodes are rectifying devices, meaning they allow current to flow easily in one direction (forward bias) and significantly block current flow in the opposite direction (reverse bias). An ohmmeter applies a small DC voltage to the component and measures the resulting current to determine resistance. When testing a functional diode: * In one direction (forward bias), the ohmmeter will show a **low resistance** because the diode conducts current easily. * When the ohmmeter leads are reversed (reverse bias), it will show a **high resistance** because the diode blocks current. Therefore, answer B correctly describes the expected behavior of a functional crystal diode. * **A is incorrect** because a functional diode's resistance is *not* the same in both directions; that would indicate a short or an open circuit, not a working diode. * **C is incorrect** because an ohmmeter *can* and *should* be used to check a rectifier; the difference in resistance is precisely how its rectifying action is verified. * **D is incorrect** because while a VTVM (or DMM) can measure voltage, an ohmmeter directly provides the critical resistance differential needed to quickly assess diode functionality.