Question

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 ______
which choice most logically completes the text?
choose 1 answer:
a a. thaliana leaves and roots are especially vulnerable to harmful bacteria.
b bacteria carried by wind are typically less beneficial to a. thaliana than soil - based bacteria are.
c many bacteria in a. thaliana leaves may have been deposited by means other than rain.
d some bacteria in a. thaliana leaves and roots may share a common source.

Explanation:

The text explains that bacteria in leaves and roots could come from soil (via rain) or wind (which can also affect soil/roots). Both explanations imply a shared source for some bacteria in leaves and roots. Option A is unsupported (no info on harmful bacteria), B has no basis (no comparison of benefits), C is inconsistent (the alternative explanations include rain and wind, not "other than rain"). So D is logical.

Answer:

D. some bacteria in A. thaliana leaves and roots may share a common source.