What protected the nile river on the east and west from invaders?

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 greek scientist created a screw to move water for irrigation?

In ancient egypt, the pharaoh collected from the peasant farmers. a. oil b. gold c. lumber d. taxes