Its called the independent variable I think.
Answer:
C) Scrubbers remove sulfur from the smoke of coal power plants.
Explanation:
Well most scrubbers in North America (U.S) coal plants are used to remove sulfur emissions from coal and lessen the formation of acid rain.
Answer:
D. It is not a superordinate goal because it did not require both pet store owners to accomplish.
Explanation:
In this case, both pet stores are benefited and therefore it corresponds to a superordinate goal.