To support the inference that honeybees, not bumblebees, are responsible for infecting the studied flowers, the best evidence from the text would be:
- All of the honeybees researchers collected were infected with both viruses.
- More bumblebees foraging close to apiaries had viruses on their outsides than had active infections.
These statements indicate that honeybees are consistently infected with viruses, which suggests they are the primary carriers of the infection, while the bumblebees show a distinction between having viruses on their outsides and active infections.