Question

however, geologists camille litty and fritz schlunegger found that cross - site variations in grain size were not associated with differences in downstream distance, though they did not conclude that downstream distance is irrelevant to grain size. rather, they concluded that sediment influx in these streams may have been sufficiently spatially diffuse to prevent the typical sorting effect from being observed. which finding about the streams in the study, if true, would most directly support litty and schlunegger’s conclusion? the streams contain several types of sediment that are not typically found in streams where the sorting effect has been demonstrated. the streams are fed by multiple tributaries that carry significant volumes of sediment and that enter the streams downstream of the sampling sites. the streams mostly originate from the same source, but their lengths vary considerably due to the different courses they take. the streams regularly experience portions of their banks collapsing into the water at multiple points upstream of the sampling sites.

Explanation:

To support Litty and Schlunegger's conclusion that sediment influx was spatially diffuse (preventing the typical sorting effect), we analyze each option:

• Option 1: Talks about sediment types, not spatial diffusion of sediment influx. Irrelevant to the conclusion.
• Option 2: Multiple tributaries with significant sediment entering downstream of sampling sites. This means sediment is coming from various (downstream) sources, leading to spatial diffusion of sediment influx. This directly supports the idea that sediment influx is spatially diffuse, preventing the sorting effect.
• Option 3: Stream lengths and origins, not related to sediment influx diffusion. Irrelevant.
• Option 4: Bank collapse upstream, which would concentrate sediment upstream, not create spatial diffusion. Contradicts the conclusion.

Answer:

B. The streams are fed by multiple tributaries that carry significant volumes of sediment and that enter the streams downstream of the sampling sites.