Critical thinking requires that a. conclusions be held constant after their initial determination b. conclusions be adjusted as necessary to incorporate new knowledge c. information from a particular source only be verified the first time the source is used d. there be a single solution to a particular problem

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.