The two pieces of evidence from the text that best support the inference that honeybees—not bumblebees—are responsible for infecting the studied flowers are:
- All of the honeybees researchers collected were infected with both viruses.
- More than 90 percent of bumblebees collected close to apiaries were infected with black queen cell virus.
These statements highlight the presence of viruses in honeybee colonies and the high infection rate of bumblebees near apiaries, suggesting that honeybees are the source of the viruses.