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Professor Smith teaches us zoology. He tells us that   36   is the most important thing in our life. But he   37   mixes us up completely.

One day, he began his lesson with these remarks: “In order to explain clearly how to dissect (解剖) frogs, I will let you see two dissected frogs. Please   38   them carefully.” Then he   39   us two pieces of things.

Kate, my deskmate, rose up and said, “I’m   40   they are two pieces of bread, Professor Smith.”

Much   41   Professor Smith said to himself in a low voice. “I have had my breakfast. But do the two pieces of bread still stay in my bag and where are the two dissected frogs that I   42   in my bag?” These words didn’t get away from our   43  .

We all   44   Jim, Professor Smith’s son. He often tells us something that happened to Professor Smith at home.

One Sunday evening, a stranger went to Professor Smith’s. Being busy   45   his lesson, Professor Smith   46   Jim to tell the stranger that he wasn’t at home. After a while, Jim   47  and said, “The stranger doesn’t   48   that you are not at home.” The Professor said   49   . “It seems that I have to go to   50   him myself.”

   51   after a long business trip, Professor Smith returned home late at night. Having no keys to the door, he knocked at the door. His wife opened it. She couldn’t see clearly the man’s   52    and didn’t   53    to have a stranger at such   54   , so she said, “I’m sorry, sir, Professor Smith isn’t at home.” “It doesn’t matter, madam. I’ll   55   tomorrow.” replied the Professor.