Question

in many agricultural environments, the banks of streams are kept forested to protect water quality, but its been unclear what effects these forests may have on stream biodiversity. to investigate the issue, biologist xingli glam and colleagues studied an indonesian oil palm plantation, comparing the species richness of forested streams with that of nonforested streams. glam and colleagues found that species richness was significantly higher in forested streams, a finding the researchers attribute to the role leaf litter plays in sheltering fish from predators and providing food resources.
which choice best states the main purpose of the text?
choose 1 answer:
a it explains the differences between stream - protection strategies used in oil palm plantations and stream - protection strategies used in other kinds of agricultural environments.
b it presents a study that addresses an unresolved question about the presence of forests along streams in agricultural environments.
c it discusses research intended to settle a debate about how agricultural yields can be increased without negative effects on water quality.
d it describes findings that challenge a previously held view about how fish that inhabit streams in agricultural environments attempt to avoid predators.

Explanation:

• Option A: The text doesn't compare stream - protection strategies between oil palm plantations and other agricultural environments. It focuses on the effect of forested streams on biodiversity.
• Option B: The text starts by stating that it's unclear what effects forested stream banks have on stream biodiversity (an unresolved question). Then it presents a study by Glam and colleagues that investigates this issue by comparing forested and non - forested streams. This option accurately captures the main purpose.
• Option C: The text is not about increasing agricultural yields or its effect on water quality. It's about the effect of forested streams on stream biodiversity.
• Option D: The text's main purpose is not to challenge a view about how fish avoid predators. It's about the effect of forested streams on species richness.

Answer:

B. It presents a study that addresses an unresolved question about the presence of forests along streams in agricultural environments.