I remember my math teacher Mr. Young very well. He stood out because the kids made fun of him. He was missing one of his fingers, and always pointed at students with his middle finger.I was not very good at English and math. No matter how hard I tried, I just could not figure out why I did not understand what all the other kids found so easy to learn.One day, I was told that if I got one more E on my report card, I would be taken to the" big prison for kids".I tried really hard for weeks. I just couldn’t understand how to make different parts of members into whole things.The day before report cards were to come out, I knew that Mr. Young would give me an E ,just like he always did.I went to Mr. Young and told him that the orphanage was going to send me to the big prison if I got another E on my report card. He told me there was nothing he could do;it would be unfair to the other kids if he gave me a better grade than I had actually earned.I smiled at him and said, "Mr. Young, do you know how the kids make fun of you because you’re missing your finger" He looked at me, moved his mouth to one side and said nothing."They shouldn’t do that to you because you can’t help having a finger, Mr. Young. Just like I can’t help not being able to learn numbers and stuff like that. "I said.The next day, when I got my report card, I tucked it into one of my books. While on the school bus, I opened it : Geography, B+ ; Mechanical Drawing, C- ; English, D- ; History, C- ; Gym, B+ ; Art, C ; Math, D-.That math grade was the most favorite one I ever received. Because I knew that someone in the world finally understood what it was like for me to be missing a finger inside my head. The reason why the boy remembers Mr. Young is that（）

A. he missed one of his fingers
B. he treated his students very well
C. he understood the boy
D. he taught his students in a special way