A mom is concerned about fluoridation in drinking water. She has read that the maximum contaminant concentration level goal for fluoride in drinking water is 4 ppm. The mom has discovered that her drinking water supply contains 0.8 ppm of sodium fluoride. I. How many milligrams of sodium fluoride are contained in one liter of drinking water containing 0.8 ppm of sodium fluoride?
II. What is the ratio strength concentration of sodium fluoride in drinking water that contains 0.8 ppm 1I. of sodium fluoride?
III. What is the ppm of fluoride in the mom's supply of drinking water? (molecular weight of NaF 42, I molecular weight of F = 19)

Which of the following best reflects what we know about how the flu virus moves between species? a) the flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.b) a flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.c) an influenza virus gains new sequences of dna from another virus, such as a herpesvirus; this enables it to be transmitted to a human host.d) an animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans.