Which choice most logically completes the text?
A
bacteria carried by wind are typically less beneficial to A. thaliana than soil-based bacteria are.
B
some bacteria in A. thaliana leaves and roots may share a common source.
C
many bacteria in A. thaliana leaves may have been deposited by means other than rain.
D
A. thaliana leaves and roots are especially vulnerable to harmful bacteria.
Explanation
Correct answer: B.
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.
Why the other choices are wrong
Choice A
Choice A is incorrect. This inference isn’t supported. The text never discusses any benefits of any kind of bacteria.
Choice C
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
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.