详解
Choice C is the best answer. In (lines 24-28"such ...bees"), the authors hypothesize that bee colonies will be susceptible to mite infestations if they do not occasionally feed on pyrethrum producing plants. In (lines 42-46"This...the"), they suggest creating a trial where a "small number of commercial honey bee colonies are offered a number of pyrethrum producing plants" to test their hypothesis.
Choices A, B, and D are incorrect because the authors do not hypothesize that honeybees' exposure to both pyrethrums and mites will cause the honeybees to develop secondary infections, that beekeepers should increase their use of insecticides, or that humans are more susceptible to varroa mites.