Based on the text, which of the following best describes the effect of Varroa mites on bees? (5 points)
a
They destroy the important crops that bees depend on to thrive.
b
They infest the bees' intestines and cause digestive and other health problems.
They make extra work for beekeepers who are fighting to keep hives healthy.
С
d
They threaten the bees directly and introduce viruses and bacteria to the hive.