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The answer is C.
The original news from Reuters (with the answer highlighted in red):

Sweaty athletes may spread hepatitis B virus
Study of wrestlers suggests vaccinating Olympians against the disease
Findings from a study of Olympic wrestlers indicate that hepatitis B virus is found in the sweat of infected individuals, and so sweating might be a way that the virus could be passed between participants in contact sports.
Bleeding wounds and mucous membranes have been implicated in hepatitis B transmission during contact sports, but until now no study had looked to see if sweat carries the virus.
Dr. S. Bereket-Yucel, from Celal Bayar University in Izmir, Turkey, tested for DNA of the hepatitis B virus in blood and sweat samples from 70 male Olympic wrestlers.
The results indicated that 9 (13 percent) of the wrestlers had the hepatitis B virus in their blood. However, these were deemed “occult” infections because no antibodies to the virus were detected in any of the wrestlers, according to the investigators’ report released Thursday ahead of print by the British Journal of Sports Medicine.
In eight of the nine participants whose blood tested positive, DNA for hepatitis B was also detected in sweat.
Based on these results, “Evidence is emerging that the incidence of occult HBV in Olympic wrestling is higher than expected and that transmission of HBV may also occur through sweat,” the researcher concludes.
“The advice of sports organizations about HBV testing should be changed,” they recommend, “making it obligatory for all participants involved in contact sports and playing under adult rules to be vaccinated against hepatitis B.”

參考資料:
Reuters

B. They say that catching the deadly liver virus through sweat is unlikely.