unit 4.Tipping Point

According to Cmbridge Dictionary, Tipping Point refers to a time during an activity or process when an important decision has to be made or when a situation changes completely. An example of a tipping point for dominican history was the dearh of Rafael Leonidas Trujillo on may 30th ,1961 after 30 years of dictatoship. 
One important part of unit 4 is listening 2,which talks about the tipping point of fighthing crime in New York,for a long time this issue concerned citizens but after the police decided to work on improving the subways , thanks to a theory called the Broken Window, crime rates started to drop.