下列生活用品所使用的主要材料属于有机合成材料的是
                     

    An old porter (搬运工人) had worked for the railway for a very long time. One morning he was standing in one of the big railway stations and waiting for travelers to ask him to help them with their luggage, when he saw a small man running toward the trains with a big bag in his hand.

    The porter watched the man for a few seconds, and the man saw the porter.

At once the small man ran up the porter and said, "Can I catch the 10：35 train to London, porter?" He was breathing very fast, and he seemed worried.

    The old porter looked at him for a moment and then said with a smile, "Well, sir, I'd like to help you, but I can't answer your question because I don't know how fast you can run along rails. You see," he explained, "the 10: 35 train to London left five minutes ago."