When there is a drought, one country will trade with another country. What caused this scarcity

The continents of africa and south america used to "fit together” like puzzle pieces. about how far back in time would you have to go to find the formation of the atlantic ocean? 600 million years 430 million years 200 million years 90 million years

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.

What does the author describe in this passage