Which qualities would researchers in psychology ascribe to "good" theories?

How and why has british society changed over the last 50 years?

Cindy is 18 years old. cindy's parents and her 23-year old brother rich are going away for the weekend. renee, cindy's best friend, is pressuring her to throw a huge saturday night party for all their friends since no one will be home. renee even asked rich if he could pick up a few kegs for them. rich brought back two kegs of beer, a bottle of vodka, and a few bottles of wine, which he hid in the basement. renee also spread the word around school for everyone to show up. cindy now has over $100 worth of alcohol hid in the basement, an empty house for the weekend, and several friends expected to show. what should she do?

Which of the following items would serve as a primary source for a historian studiying the american civil war