完形填空

　　It must have been about two o'clock in the morning when I was woken suddenly by a loud banging noise. It was such a 1 night that I did not have the idea of getting up, so I sat in bed and 2 . Since I heard nothing more, I thought that the sound must have come from the street. I was just 3 the bedclothes over my head to go back to sleep, when there was another loud bang. The sound was so strange that this time I 4 out of bed at once.

　　I put on my dressing-gown and tip-toed (踮着脚尖走) 5 , feeling my way carefully. I found the drawing-room door open and could not remember if I had 6 it like that. The room was lit up by a pale red glow (火焰) from the fire which was slowly 7 . I quickly turned on the lights but could see nothing unusual. I felt rather ashamed (羞愧) of my 8 act. And I began climbing the stairs when I heard the same noise again. It came clearly from 9 . I ran upstairs and went into all the bedrooms one after another, but there was nothing that could 10 have made such a sound. I went across to one of the 11 . It was so cold outside that ice had formed on the windowpanes. I scraped (刮) it away and looked 12 on the garden below. Lamps from the street in the distance 13 enough light to see by. It was snowing heavily and a thick white 14 covered everything. The branches of the trees looked like white arms against the night sky. There was certainly no 15 that anyone had been walking in the garden for it would have been easy to make out 16 . As I was beginning to feel 17 , I went to my room, sat on my bed and waited to see if the noise would 18 again. It did－from directly above me. Just then I did understand, the water in the 19 leading to the tank in the attic (顶楼) was beginning to 20 and the pipes were protesting (反抗) loudly!

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