She was afraid that unless the train speeded up she would lose her __to Scotland.

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.