Mr. Jackson worked in a hospital．A lot of patients（病人） went to see him and he was very busy and had little time to rest in the daytime．One night, when he looked over the last patient, it was five to one．He was too tired to say a word and lay down at once．As soon as he fell asleep, a farmer began to knock at the door and got him up． “My wife is ill．”shouted the farmer,“Please go and look her over．”Mr. Jackson had to go out with the farmer．It was the coldest night of the year and the road was covered（覆盖） with snow and ice．The farmer lived far away from the town and they went through a forest, crossed two rivers and a mountain．It took them three hours to get to the short, small house．And they were both tired, cold and hungry． The woman stayed in bed．She looked fine．Mr. Jackson looked her over carefully and found there was nothing serious with her．He became angry．He called the farmer out and said,“Your wife is strong and healthy, you know．Why did you ask me to come here late at night?”“I’m sorry, sir．”said the farmer,“My wife never does anything at home．I thought she was ill．We’re poor．In the day, When you’re busy, I can’t go for you．If you came to look her over at night when you’re free, we’ll pay you nothing．” 

The farmer went for Mr. Jackson very late at night because（） ．

A.he wanted to play a joke on him

B.he was busy in the day

C.his wife was going to die

D.he wanted to save some money