She was afraid that unless the train speeded up she would lo

connection 按照《牛津高阶英语词典》上的解释是：a train,bus or plane at a station or an airport that a passenger can take soon after getting off another in order to continue their journey 转车；转机；联运
这句话的意思是：她担心如果火车不开快一点的话,她就来不及转另一班火车去苏格兰了.所以选D.