【正确答案】 A

【答案解析】HAV is predominantly transmitted by the ingestion of fecally contaminated food. Transmission is more likely to occur with poor hygiene, crowded conditions, and poor sanitation. Hepatitis B and C may be transmitted through exposure to contaminated blood and blood products. Sexual activity with an infected partner and sharing contaminated needles or syringes may also transmit hepatitides B and C.