What did the clean air act allow citizens to do that no previous u. s environmental law has allowed

Galaxy whose shape seems different follow no set pattern are classified as

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

Explain why biological control methods are generally environmentally superior to chemical pest control methods.