阅读下面短文，从短文所给各题的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项.

       Some of the saddest moments I spend as a veterinarian（兽医）are those spent with the owners assisting the transition（过渡）of my animal patients from this   36  to the next .When living becomes a   37  ,whether from pain or  38  of normal functions ,I can help a family by ensuring that their beloved pet has an easy passing. Making this final decision is   39  ,and I have often felt   40  to comfort the sad owners.

       But that was  41  .I met Shane.

       I had been called to examine a ten-year-old blue dog named Belker who had  42  a serious health problem. The dog’s owners—Ron ,his wife, Lisa ,and their little boy ,Shane—were all very   43  to Belker and they were hoping for a miracle（奇迹）. I examined Belker and found he was dying of cancer.

       I told the family there were no miracles left for Belker, and   44  to perform the euthanasia（安乐死）procedure for the old dog in their home. As we made the arrangements, Ron and Lisa told me they thought it would be  45  for the four-year-old Shane to   46  the procedure. They felt Shane could learn something from the   47  .

       The next day , I felt the familiar catch ,in my throat as Belker’s family surrounded him. Shane seemed so  48  ,petting the old dog for the last time ,that I wondered if he   49  what was going on.

       Within a few minutes ,Belker  50  peacefully away . The little boy seemed to  51  Belker’s transition without any difficulty or confusion. We sat together for a while after Belker’s death , wondering aloud about the sad fact that animal lives are  52  than human lives.

       Shane ,who had been listening quietly ,cried out , “I know why.”

         53  ,we all turned to him . What came out of his mouth next impressed me so much—I’d never heard a more  54   explanation.

       He said. “Everybody is born so they can learn how to live a good life—like loving every—body and being nice, right ?” the four-year-old child continued, “Well ,animals  55  know how to do that ,so they don’t have to stay as long.

36．A．family      B．house       C．home        D．world

37．A．burden      B．pleasure    C．difficulty  D．problem

38．A．gain        B．loss        C．recovery    D．decrease

39．A．fun         B．shocking    C．painful     D．painless

40．A．powerful    B．powerless   C．willing     D．unwilling

41．A．before      B．after       C．when        D．until

42．A．infected    B．developed   C．improved    D．solved

43．A．applied     B．adapted     C．addicted    D．attached

44．A．hurried     B．attempted   C．offered     D．afforded

45．A．good        B．terrible    C．bad         D．horrible

46．A．stop        B．observe     C．perform     D．assist

47．A．transition  B．experience  C．performance D．procedure

48．A．calm        B．happy       C．sad         D．nervous

49．A．enjoyed     B．hated       C．found       D．understood

50．A．slipped     B．walked      C．ran         D．died

51．A．accept      B．refuse      C．receive     D．support

52．A．richer      B．poorer      C．shorter     D．longer

53．A．Surprised   B．Frightened  C．Excited     D．Disappointed

54．A．surprising  B．interesting C．comforting  D．amazing

55．A．still       B．already     C．never       D．perhaps