单选题：回答题It was Clark's first visit to London Underground Railway.

回答题
It was Clark's first visit to London Underground Railway. Against 36 advice of his friends, he decided to go there after 5 o' clock in the afternoon. This is a bad time to 37 in London, because numerous people go home from work 38 this hour. He had to join a long 39 of people who were waiting for tickets. When his turn came, he had some difficulty in making himself 40 by the man selling tickets. However, he got the right ticket 41 the end and, by asking people the 42 , he also found the right platform. It was packed tight 43 people. He did not 44 to get on the first train, but he was 45 to move nearer to the edge of the platform so as to be in a better 46 to get on the next one.
When this train came in, Clark was 47 forward on to the train by the 48 of people from behind. The doors closed and the train 49 off. He was unable to see the names of the stations where the train stopped, but he knew that the station he wanted was the sixth 50along the line. When the train got to the sixth station, Clark got off, feeling good that his 51 had been so easy. But he suddenly 52 that he had come to a station he had never heard of He explained his difficulty to a man who was standing on. the platform. With a 53 on his face, the man 54 Clark that he had caught a train going in the opposite 55。
A．an
B．some
C．any
D．the