根据短文内容，从方框中选出能填入空白处的最佳选项。(选项中有两项为多余选项) Saying Goodbye Many people were waiting for the train. Some were reading newspapers and some were saying goodbye to their friend． Doctor Smith, Mr. Lee and Mr. Brown were talking so happily that ____16____ Then the guard called loudly, “The train is going to leave. ____17____ The three men heard the guard and two of them jumped onto the train quickly before it moved. One was left behind. It was Dr. Smith. He ____18____ The guard came to him and said, “Don’t worry. ____19____ ”“I know.” Dr Smith said，“ ____20____ My friends only came to say goodbye to me. ” A. But it is my train. B. they didn’t know the train was going to leave. C. was very excited. D. Hurry up, please. E. looked very sad. F. The next train will come in ten minutes. G. Take your time.

文摘属于（）。

A．零次文献

B．一次文献

C．二次文献

D．三次文献

E．四次文献