Question

in the mid - 1900s, lake washington near seattle, washington was primarily being polluted with which smelly pollutant?
oil and grease
fertilizers
pesticides
untreated sewage

Explanation:

In the mid - 1900s, Lake Washington near Seattle was primarily polluted by untreated sewage which is a smelly pollutant. Oil and grease, fertilizers, and pesticides are not the main smelly pollutants in this case.

Answer:

untreated sewage