When Researchers Examined the Effects of Withholding Nitrogen from Bradyrhizobium

Multiple Choice

When researchers examined the effects of withholding nitrogen from Bradyrhizobium japonicum, they used a "split root" treatment in which half of a soybean plant's root mass received gaseous nitrogen, whereas the other half did not. Why did the researchers use this split-root treatment?

A) They were economizing on experimental soybean plants.
B) They were testing whether different parts of the root react differently to the absence of nitrogen.
C) They were testing the range of nitrogen in which soybean plants can thrive.
D) They were testing whether the potential "retaliation" against cheating symbionts was specific to root nodules that did not fix nitrogen.