Which three choices are positive effects of the pax romana ("the time of roman peace"), which lasted from around 27 bc until ad 180? a) slavery was abolished, the colosseum was built, and the empire expanded. b) christianity was banned, the society became classless, and the colosseum was built. c) the colosseum was built, the empire expanded, and more public works were constructed. d) the emperors waged wars with surrounding territories, more public works were constructed and the fewer farmers were needed.