题目

Monthly Talks at London Canal Museum Our monthly talks start at 19:30 on the first Thursday of each month except August. Admission is at normal charges and you don’t need to book. They end around 21:00. November 7th The Canal Pioneers, by Chris Lewis. James Brindley is recognized as one of the leading early canal(运河) engineers. He was also a major player in training others in the art of canal planning and building. Chris Lewis will explain how Brindley made such a positive contribution to the education of that group of early“civil engineers”. December 5th Ice for the Metrop如图，已知，在四边形ABCD中，AD∥BC，BD平分∠ABC，∠A=120°，CD=4cm，∠ABC=∠DCB，求BC的长．