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Biologist Natacha Bodenhausen and colleagues analyzed the naturally occurring bacterial communities associated with leaves and roots of wild Arabidopsis thaliana, a small flowering plant. The researchers found many of the same bacterial genera in both the plants’ leaves and roots. To explain this, the researchers pointed to the general proximity of A. thaliana leaves to the ground and noted that rain splashing off soil could bring soil-based bacteria into contact with the leaves. Alternatively, the researchers noted that wind, which may be a source of bacteria in the aboveground portion of plants, could also bring bacteria to the soil and roots. Either explanation suggests that blank
Which choice most logically completes the text?
Explanation
Choice B is the best answer. Both explanations suggest that the bacteria come from the same place: either they come from the ground and make their way to the leaves, or they come from above the ground and make their way to the roots.
Choice A is incorrect. This inference isn’t supported. The text never discusses any benefits of any kind of bacteria. Choice C is incorrect. This conflicts with the text. One of the theories is that the bacteria in the leaves were deposited by rain splashing off soil. Choice D is incorrect. This inference isn’t supported. The text only discusses “naturally occurring” bacteria. It never mentions either the harms or benefits of these bacteria.