Self-study
In a vast ocean region, phosphorus levels have doubled in the past few decades due to agricultural runoff pouring out of a large river nearby. ███ ██████████ ██████████ ███ ██████ ██ ████████ ████ ███ █████ ████████ ████████ ████████ ████ ██ ███ █████ ██████ █████ ████████ ██████ █████ █████████ ██████ ██ ███ ████████ ███ ██ ███ █████████ ██████ ██████████ ███ ████ ███ ███████ ██ ████ ███████
Summary
Agricultural runoff from a river has caused phosphorus levels to double in an ocean region.
The phosphorus causes the stimulation of plankton growth near the ocean surface.
The plankton decay and fall to the floor, where bacteria eat them and consume oxygen.
This oxygen depletion means that few fish can survive in the region.
Very Strongly Supported Conclusions
The agricultural runoff and the phosphorus contribute to the plankton growth, the oxygen depletion, and the fishes’ inability to survive in the region.
10.
Which one of the following ███ ██ ████████ ████████ ████ ███ ███████████ ██████
a
The agricultural runoff ███████ ███ ██ ███ █████ ███████████ ██ ███ ██████ ██ ████████ ████ ███ █████ ████████
Very strongly supported. The agricultural runoff contributes to the growth of plankton because it caused phosphorus levels to double, which in turn caused the stimulation of plankton growth.
b
Before phosphorus levels ███████ ██ ███ █████ ███████ ████ ████ ████ ████ ██ ███████ ██ ████ ███████
Unsupported. Higher phosphorus levels have contributed to fish being unable to survive in the region. But we don’t know whether most fish could survive before phosphorus levels doubled.
c
If agricultural runoff ██████ ███████ ███ ██ ███ ██████ █████ █████ ██ ██ ████████ ██ ███ █████ █████ █████████ ████████ █████████
Unsupported. If the agricultural runoff stopped, there might be fewer plankton and fewer bacteria devouring decaying plankton. But we don’t know that there would be no bacteria devouring decaying plankton.
d
The quantity of ████████████ ██████ ███████ ███ ██ ███ █████ ███ ███████ ██ ███ ████ ███ ████████
Unsupported. Agricultural runoff has caused phosphorus levels to double in the past few decades. This doesn’t mean that the runoff itself has doubled in the past few decades.
e
The amount of ██████ ██ █ ████ ██ █████ ██ ██ ███████ █████████ ████████████ ██ ███ █████ ██ ██████████ ██ ████ ████ ██ ██████
Unsupported. It’s true that in this specific region, the water’s oxygen levels have decreased as its phosphorus levels have increased. But this is due to a particular chain of events. We don’t know that oxygen and phosphorus levels are inversely proportional in general.