In one social psychological experiment, each participant is introduced to an attractive stranger. however, these "strangers" are secretly working for the experimenter. the strangers are called:

confederates a person one works with, especially in something secret or illegal; an accomplice. A confederacy is a political union. The most famous American confederacy consisted of the southern states who fought the northern states in the American Civil War.

Clean air provides nitrogen

Water(like when there is a hurricane)some foods(not enough for everyone)