Totalitarian Propaganda can controlled well educated people by conveying the regimes beliefs, almost forcing it down their subjects throats.
So when it works it usually shows an "Evil" or "Enemy" of the state, and obviously without proper methods of evaluating the truth decent people will believe it for example look at the DPRK or Iran.
They should know about the boston massacre and the boston tea party because they where the key events leading to the american revolution war
Their is your answer the term her would not make any sense in this sentence but their would because asking did either of the sisters bring their umbrella and the term their belongs to both of the sisters