What substance is necessary for human life is produced by ocean organisms that photosynthesize

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

The negative change found inside the plasma membrane is created by potassium ions sodium ions hydrogen ions chlorine ions

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.