Which type of rock most likely formed layer J

Could someone me with number one you

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

And give a detailed description! scientist observes the boundary between two tectonic plates for a decade and finds that no new volcanoes have formed over the course of her investigation. does this result support the theory of plate tectonics? why or why not?