The answer is the liver. Milady states it directly: hepatitis "is a bloodborne virus that causes disease and can damage the liver." Hepatitis is one of the specific bloodborne pathogens the Sanitation curriculum names by risk category, alongside HIV — both are reasons barbers follow strict blood-exposure protocols for any nick or cut.
Heart, kidney, and lungs — the other choices — aren't the organ hepatitis is known for damaging; "hepat-" itself is the medical root for liver, which is a useful memory anchor for this specific exam question.
Milady Standard Barbering, 6th ed., Ch. 4 (Infection Control), p. 69: "Hepatitis... is a bloodborne virus that causes disease and can damage the liver."
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