通读下面短文，掌握其大意，然后在各题所给的四个选项(A，B，C，和 D)中选出一个最佳答案。
One summer evening I was sitting by the open window， reading a good novel. I was so 1 the story I was reading that I didn't 2 that it was getting dark. When I realized that it was too dark for me to read 3， I put the book down and got up to turn on the light. Just then I heard someone 4， "Help! Help!" It seemed to come from the trees at the end of the yard. I looked out but it was too dark to see anything clearly. Almost immediately I heard the cry again. It sounds like a child， but I could not 5what someone would be doing in our backyard， unless one of my neighbor's children had climbed a tree and had not been able to 6.
I decided that I should go out and have 7 in the yard， just in case someone was8. With a flashlight and a stick in my hands， I went out into the yard. Once again I heard the cry and this time there was no doubt that it came from the trees at the far end of the yard. "Who is there?" I 9 as I walked across the yard towards the trees. But there was no 10. With the help of my flashlight， I 11 all over that end of the yard， including the branches of the trees. There was no 12 of anybody or anything. I came to the conclusion that my 13 made fun of me， probably nothing is happening there.
I had to go back into the house and sat down to read my book again. Not long after that， I was 14 by the loud cry of "Help! Help!" This time it was from right behind me! I dropped my book and jump up. There， sitting on the table was my neighbor's large green and red 15.
