1. A psychologist is interested in learning more about how children interact with each other during the school day. The psychologist is particularly interested in discovering the ways in which children behave when they think they are not being watched. What research method would be best used to conduct this type of research

situational research

Explanation:

Situational research: In psychological research, the term "situational research" is described as a collection of different methods that are being used by researcher or investigator to analyze the external and internal factors responsible for a person to behave in certain ways. The research can further involve oneself in the part of the group he or she wants to examine or else he or she can provide the children with a specific situation to evaluate and analyze their response towards the same.

In the question above, the given statement represents situational factors.

by using  production possibilities graph.  opportunity costs are key expenses in financial matters and are utilized as a part of registering money saving advantage investigation of a venture. such expenses, be that as it may, are not recorded in the record books but rather are perceived in basic leadership by processing the money costs and their subsequent benefit or misfortune.

the answer to your question is,

old stone age.

-mabel < 3