题目内容：
请阅读短文，完成第小题。 There was a time in my life when beauty meant something special to me. I guess that would have been when ! was about six or seven years old, just several weeks or maybe a month before the orphanage(孤儿院) turned me into an old man.
I would get up every morning at the orphanage, make my bed just like the little soldier that I had become and then I would get into one of the two straight lines and march to breakfast with the other twenty or thirty boys who also lived in my dormitory.
After breakfast one Saturday morning I returned to the dormitory and saw the house parent chasing the beautiful monarch butterflies who lived by the hundreds in the bushes scattered around the orphanage.
I carefully watched as he caught these beautiful creatures, one after another, and then took them from the net and then stuck straight pins through their head and wings, pinning them onto a heavy cardboard sheet.
How cruel it was to kill something of such beauty. I had walked many times out into the bushes, all by myself, just so the butterflies could land on my head, face and hands so I could look at them up close.
When the telephone rang the house parent laid the large cardboard paper down on the back cement (水泥) step and went inside to answer the phone. I walked up to the cardboard and looked at the one butterfly who he had just pinned to the large paper. It was still moving about so I reached down and touched it on the wing causing one of the pins to fall out. It started flying around and around trying to get away but it was still pinned by the one wing with the other straight pin. Finally its wing broke off and the butterfly fell to the ground and just trembled.
I picked up the torn wing and the butterfly and I spat on its wing and tried to get it to stick back on so it could fly away and be free before the house parent came back. But it would not stay on him.
The author set the living butterfly free because A．he liked it very much
B．he had sympathy for the beautiful butterfly
C．he couldn't bear a butterfly dying in his favorite bushes
D．its wing broke off
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