50. D 考查细节理解。根据文章第一段中的Unfortunately, the only one train a day back to my home in Sydney had already left."可知,作者错过了唯一的那趟回家的火车。故答案为D
51. A 考查细节理解。根据文章第二段中的"he helped me find a lift home"可知,Gordon帮助作者搭上了回家的便车。
52. D 考查细节理解。根据文章第三段中的"I thought it was another chance to repay someone for the favour I'd been given decades earlier."可知,答案为D。
53. A 考查写作意图。通读全文可知,作者想通过这个故事告诉大家:有时付出会得到回报。