Mr.Henry lived in a small village with high mountains all ar

Mr.Henry lived in a small village with high mountains all around it．All day he worked on his farm and never went to the city．Sometimes he went to the town which is not far away to buy something,but he always walked there and never took a bus or a train．His wife died after his only daughter was born．When the girl,Ann,grew up,she left her father and went to college．Four years later Ann passed all her examinations and found work in a hospital in the capital．As she was busy,she had no time to go back to see her father．But she missed her father very much．So she
wrote to his father and asked him to come to the capital．
When Mr.Henry heard from his daughter,he was quite happy and was soon ready to set off．The next day,as soon as he got to the station,he rang Ann up and told her the train he would take．At eight in the morning the train arrived at the Capital Station．Mr.Henry had spent about sixteen hours on the train．As soon as he got off,he saw his daughter standing there to meet him．Ann ran up to him and found that her father looked pale．
“What’s the matter with you．Dad?”Ann asked in surprise．“Do you feel unwell?”
“Nothing,”answered Mr.Henry．“I’m just not used to sitting backwards(背朝前) in the train．“Oh,dear,” laughed the girl．“Why didn’t you exchange seats with the man opposite to you?”“How can I do that?”answered Mr.Henry．“No man sat opposite to me!”
75．Mr.Henry didn’t exchange seats because ________.
A．there was no man opposite to him
B．he had fallen asleep on the train
C．he hadn’t known he had been able to do so
C
有点理解不了,
当他女儿问为什么没与对面的人调换个位置,他说"How can I do that?”answered Mr.Henry．“No man sat opposite to me!

他的意思是,既然女儿让他与对面的人换个座位,那么前提就是：对面有人.但是,当时的情况是：他的对面没人,那么按照他的逻辑,他就认为没法换（因为对面没人）.这个故事的笑料就在此.
（不知道你能懂我的意思吗?）