Alaskan fish are some of the least contaminated in the world, and the salmon population continues to thrive despite the yearly fishing. How do they do it? Please give some sites! Need help urgently!

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 tubes transporting minerals and water upward are called ?

Which of the following is a period in the paleozoic era? devonian cambrian permian all of the above