In an experiment, a scientist decides to study the effect of exercise on cholesterol levels in people. He studies two set of people—those who exercise every day for an hour and those who don’t exercise at all. In this case, the statement that people who exercise for an hour may have lower cholesterol levels is (blank). To test this statement, the scientist would measure cholesterol levels in exercisers and non-exercisers. The cholesterol levels would be (blank).

Waste water from industries and domestic sources can be treated by chlorination or ultraviolet radiation. there are pros and cons to using either chlorine or uv radiation to kill harmful microorganisms. what is one reason chlorination would be preferred over ultraviolet radiation? a) chlorine only eliminates visible impurities and is ineffective against microorganisms. b) chlorine not only kills bacteria but provides a residual effect on returning microorganisms. c) uv radiation can be used only to treat drinking water and is ineffective in treating waste water. d) ultraviolet radiation is more effective