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A
Only voltage
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B
Voltage, current, and resistance (and often additional functions like continuity, capacitance, frequency, and temperature)
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C
Only current
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D
Only power
Why this is the answer
Multimeter: combination instrument measuring multiple electrical quantities. Functions: (1) DC VOLTAGE — typical ranges 200mV to 1000V; connect probes in PARALLEL across the points being measured (DON'T break the circuit); high input impedance prevents disrupting the circuit; (2) AC VOLTAGE — for measuring household power, transformers; (3) DC CURRENT (Amperes) — typical ranges μA to 10A; connect probes in SERIES (break the circuit and route current through meter); very low resistance shunt; HIGH current ranges have separate input jack; using current setting across voltage = SHORT CIRCUIT, can blow fuse and damage meter; (4) AC CURRENT — less common in basic meters; clamp meters measure without breaking circuit by sensing magnetic field around wire; (5) RESISTANCE — typical ranges 200Ω to 200MΩ; meter applies small voltage and measures resulting current; MUST measure with power off (live circuits give wrong readings or damage meter); (6) CONTINUITY — beeps if resistance is very low (typically <50Ω); used to verify wire connections, switch closures, fuses intact; (7) DIODE TEST — checks forward voltage drop and reverse blocking; (8) CAPACITANCE — measures capacitor value; better meters; (9) FREQUENCY — measures Hz of AC signal; (10) TEMPERATURE — with thermocouple probe; (11) DUTY CYCLE — percentage of time signal is high in a PWM signal. Types: ANALOG — needle deflects; less common today but useful for trends; DIGITAL — digital readout; most common; AUTORANGING — automatically selects appropriate range. Safety: rated voltage categories (CAT I, II, III, IV) — higher categories handle higher transient voltages; always check rating matches application; use insulated probes; don't exceed meter's max voltage/current; replace fuses with same rating. Common errors: (1) Trying to measure resistance with circuit powered; (2) Using current range across voltage source (short circuit); (3) Exceeding meter ratings; (4) Wrong probe placement. Quality matters: cheap meters may give wrong readings or fail dangerously; reputable brands (Fluke, Klein, Amprobe, Triplett) have proper safety design. ASVAB EI may show multimeter readings and ask about interpretation.
Source: ASVAB EI, Multimeters