Most of the research on adolescents has been carried out with samples.

Most of the research on adolescents has been carried out with white, middle class samples.

To add, research on adolescence uses both quantitative and qualitative methodologies applied to their cognitive, physical, emotional, and social development and behavior. A popular research that tackles this can be found in the book, Journal of Research on Adolescence.

every society, in order to meet the needs of it's people, has to answer three basic questions:

- what should we produce?

- how should we produce it?

- for whom should we produce it?

this questions must be answered in order to, option b, aid in production decisions.

every country can't produce everything, no matter how rich their land is. it may be a matter of technology, resources or geographical conditions. so, these three questions must be resolved in order to get the most of the production of each land.

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the use of electrical signals that transit messages is know as