Answer:
longitudinal study
Explanation:
Longitudinal studies are typically observational studies, as they are usually limited to observing the sample elements without manipulating factors that may alter the variables of interest. For example, to verify the effectiveness of a treatment for posttraumatic stress disorder, researchers can analyze the psychological status of the study subjects before and after treatment. This is because a longitudinal study is one that evaluates how the variables behave in the research participants over a given period of time.
Another example of this type of study is what is happening to Alice, where researchers ask her to answer a questionnaire each year so they can assess how her attitudes and preferences have changed over the course of a year.
Economists usually call an industry an oligopoly if: the four largest firms produce at least 70–80 percent of the output.
Organized labor, or trade union, is an organisation of workers which has as its aim to fight for and improve the workers' rights. <span>Out of the 4 options only D. National Education Association is an organisation of workers- this is the correct answer. </span>
The other organisations don't work for workers' rights, but instead for environment protection (C), the right to keep arms (A) and B is a media network.
