根据短文回答 31～35 题。
Sleepless at Night
It was a normal summer night. Humidity (湿气) hung in the thick air.
I couldn't go to sleep, partly because of my cold and partly because of my expectations for the next day. My, mum had said that tomorrow was going to be a surprise.
Sweat stuck to my aching body. Finally, I gathered enough strength to sit up. I looked out of my small window into the night. There was a big bright moon hanging in the sky, giving off a magic glow.
I couldn't stand the pressure anymore, so I did what I always do to make myself feel better. I went to the bathroom and picked up my toothbrush and toothpaste. I cleaned my teeth as if there was no tomorrow. Back and forth, up and down.
Then I walked downstairs to look for some signs of movement, some life. Gladiator, my cat, frightened me as he meowed (喵喵地唱出) his sad song. He was on the old orange couch (长沙发), sitting up on his front legs, waiting for something to happen. He looked at me as if to say, "I’m lonely, pet me. I need a good hug (紧抱).”Even the couch begged me to sit on it.
In one movement I settled down onto the soft couch. This couch represented my parents' marriage, my birth, and hundreds of other little events.
As I held Gladiator, my heart started beating heavily. My mind was flooded with questions: What's life？ Am I really alive？ Are you listening to me？ Every time I moved my hand down Gladiator's body, I had a new thought; each touch sang a different song.
I forgot all about the heat and the next day's surprise. The atmosphere was so full of Warmth and silence that I sank into its arms. Falling asleep with the big cat in my arms, I felt all my worries slowly move away.
第 31 题 The author of the passage could not go to sleep partly because（）

A. it was too cold
B. it was too dry
C. he had a cold
D. he had a fever