题目内容：
阅读下列短文，回答题。Dick was a clever college student, but his parents were poor, so he had to work after class and during his holidays to get enough money for his studies.
One summer he got a job in a butcher's shop during the daytime, and another in a hospital at night. In the shop, he learned to cut and sell meat. He did so well that the butcher(肉电老板) often left him to do all the things while the butcher went into a room behind the shop to do the accounts(算账). In the hospital, of course, Dick was told to do only the easiest jobs. He helped to lift people and carry them from one part of the hospital to another. Both in the butcher's shop and in the hospital,Dick had to wear white clothes.
One evening in the hospital, Dick had to help to carry a woman from her bed to the operating room. The woman already felt frightened when she thought about the operation. When she saw Dick coming to get her, she felt even more frightened.
"No! No!" she cried. " Not my butcher! I won't let my butcher operate on me!" With these words she fainted (晕倒).
Dick had to work after class and during his holidays because__________. A．his parents told him to make more friends
B．he wanted to become a rich man
C．he couldn't go on with his studies without enough money
D．he had nothing to do at home
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