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.
- All the infected flowers researchers picked and tested were close to apiaries.
These statements imply that honeybees, which were confirmed to be infected, are likely the source of the infections found in the flowers that were close to the apiaries.