In a laboratory study, 100 rabbits in an experimental group were injected with serum D and 100 rabbits in control group were injected with harmless sugar solution. In one week. 50% of experimental group contracted jungle fever, a very contagious disease. Therefore jungle fever must be caused by a substance similar to substances in Serum D. This argument would be strengthened if:

• A. Normal rate of jungle fever in rabbits is less than 1%
• B. 50% of control group rabbits had also contracted jungle fever in the same time
• C. The Serum D has substances extracted from a poisonous jungle flower
• D. The blood samples of fever victims invariably contain a highlevel of toxic substances also found in Serum D