Which of the following describes an outcome of water scarcity in a community? a) More imports and exports b) Loss of industries and jobs c) Emigration of people into the area d) Increased housing and construction

Coliforms are commonly used as an indicator of drinking water quality. As we discussed, in March and April of 1993 there was a major outbreak of gastrointestinal illness in Milwaukee, Wisconsin caused by contamination in the public drinking water supply.  As summarized by MacKenzie et al.1, “throughout the period from February to April 1993, samples of treated water from both (water treatment) plants were negative for coliforms and were within the limits set by the Wisconsin Department of Natural Resources for water quality.”  Why, in this case, did coliforms remain at acceptable levels despite water contamination that resulted in over 400,000 cases of gastrointestinal illness?

Please help me to answer part a-b Thank you    a) Define the two terms "keystone species" and "trophic cascade." b) Give an example of a keystone species that causes a trophic cascade when removed from its ecosystem. Name the species and briefly describe what happens when it is removed.

Is it  A agricultural  B fractural C industrial D municipal