Which of the following is true about impervious building materials? a. impervious surfaces prevent pollutants from entering the water supply. b. vegetation and gravel are common impervious materials. c. having fewer impervious surfaces improves water drainage. d. all of the above

Researchers randomly divide participants into groups. each group takes a different amount of omega-3 fatty acid supplements daily for a month. one group receives a placebo. the researchers measure the impact on cholesterol levels in the blood. what is the purpose of random assignment in this experiment? a, to produce treatment groups with similar characteristics b, to ensure that all people with high cholesterol have an equal chance of being selected for the study c, to increase the accuracy of the research results and prevent skewness in the data

9. the history of life on earth is recorded in

What will happen if two of the base pairs of the stand of the dna are switched