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AP® Environmental Science

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River Water Testing

APES-VGJFXW

​A city has tested the water in a nearby river. The following data were recorded:

pH DO ammonia E. coli
River 7.54 9.4 mg/L 3.8 mg/L 515 colonies/100 mL
Standard 6.5-8.5 4 mg/L 5.0 mg/L 235 colonies/100 mL

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Based on this report, what will the city's residents be most interested in improving?

A

Decreasing the pH which has been affected by acid rain and which could cause a fishkill.

B

Decreasing the ammonia which has increased due to industrial waste, and which can cause cancer in humans who use the river as a drinking water source.

C

Decreasing the DO which is too high for the wildlife that depend on the river for drinking water.

D

Decreasing the E. coli which is high due to agricultural runoff and combined sewer overflows and which can cause illness in people who swim in the river.

E

Nothing needs to be changed, since the water testing data shows all variables are within healthy levels.