The hepatitis B virus is common in China relative to other countries in the region. The disease can easily be prevented through vaccination, regulation of barbershop and manicure practices, and health education. Yet, the incidence of this disease continues to rise in China, while it remains stable or is falling in China's neighboring countries. Which of the following, if true, would best explain the situation described above? ['Twenty years ago, a complete and accurate study by an international health agency revealed that the incidence of hepatitis B was much higher in China than in neighboring countries.', 'Medicine is socialized in China but not in neighboring countries, meaning that more people in China have access to health care than in neighboring countries.', 'To speed its industrial development and the education level of its citizenry, China does not burden small businesses with many regulations nor does it require its school population to have vaccinations, as neighboring countries do.', 'Illegal drug use has risen faster in China than in neighboring countries.']