阅读下面的短文，掌握其大意，然后从短文后各题所给的A. B. C. D四个选项中，选择最佳选项。
On the plane to London, an old man asked an air hostess (空姐) for a cup of water to take medicine (药) . She told him that she would bring him the 1 soon.
Twenty minutes 2 when the old man asked service again, the air hostess heard. She was kept so busy that she 3 to bring him the water, so the old man couldn't take his medicine on time. She ran to him with a cup of water, but he 4 it.
In the following hours on the flight, when the air hostess passed the old man, she would ask him with a smile (微笑) , "Is there anything I can do 5 you, sir?" But the old man read the book all the time and 6 relied to her .
7 the plane arrived in London, the old man asked the air hostess to hand him the passenger's booklet (意见簿) . She knew that he would8 bad words, and those words might make her 9 the job. Although she felt so upset, she 10 handed it to him with a smile.
After she got off the plane, the air hostess 11 the booklet. To her surprise, the old man wrote, "On the flight, you asked me if I needed 12 twelve times in all. How can I refuse 13 twelve smiles?"
That's right! The twelve smiles 14 the air hostess moved (感动) the old man and of course she wouldn't lose her job! She was busy with service for quite a few hours, but she felt 15 at the moment.
B. 
C. 
E. 
F. 