Question

To provide clean running water, Philadelphia
a. purchased clean water from other major cities
b. controlled the flow of its streams with underground pipes
c. built a water factory where people brought wastewater for cleaning
d. urged its residents to mix salt with water to destroy bacteria before drinking

Answer 1

To provide clean running water, Philadelphia "a. purchased clean water from other major cities" although it should be noted that this was a temporary solution. 

Answer 2

b is the answer I took the test and got 100%