What kind of trade occurs only when nations expect to gain something? absolute, voluntary, specialized, or comparative?

Asociologist wants to study a culture that occurs in some women’s prisons: “state families,” in which individual prisoners take on certain roles within a group of like-minded prisoners. there is previous evidence that younger prisoners will use older inmates who play the roles of grandparents as a resource before they will turn to staff for and advice. the lieutenant in charge of a dorm of long-term prisoners offers to gather volunteers to speak to the researcher and also offers to vouch for the integrity of the researcher. the use of this staff is: a valid use of a statistical technique referred to “snowball sampling” wherein the inclusion of the first subject leads to the recruitment of another one subject. a useful tactic in obtaining a sample of prisoners who both meet the criteria and who will be honest with the researcher. wrong and is prohibited; subject selection needs to be free from intervention by prison authorities or prisoners. acceptable only when the researcher’s irb grants a special waiver.