What is the difference between a pre-zygotic and a post-zygotic barrier to reproduction?

Cultures of the lake of the ozarks water samples were grown on enrichment media for identification. however, these organisms are present to some degree in all samples. an important question from a clinical perspective is whether or not there is a significant increase in the fecal coliform populations that would put people's health at risk. if you were part of the team investigating this outbreak, how would you best enumerate the fecal coliform threat? view available hint(s) cultures of the lake of the ozarks water samples were grown on enrichment media for identification. however, these organisms are present to some degree in all samples. an important question from a clinical perspective is whether or not there is a significant increase in the fecal coliform populations that would put people's health at risk. if you were part of the team investigating this outbreak, how would you best enumerate the fecal coliform threat? direct microscopic counts filtration count culture serial dilution count culture plate count culture

Ineed to know why d is the correct answer asap

According to piaget, children have acquired the cognitive skill of conservation when they're able to a. understand that six ounces of liquid in a jar and six ounces in an elongated tube are equal. b. understand the viewpoint of other people. c. relate objects around them to their own needs. d. realize that the term heavy describes an object one way and the term big describes it another way. it is not b nor c. did this 2 x wrong..