三、完型填空（共20小题，每小题1.5分，共30分）
阅读下面短文，掌握其大意，然后从31~50各题所给的四个选项（A、B 、C 、D）中，选出最佳选项，并在答题纸上将该选项标号涂黑。
I am a teacher. Last Monday, at the beginning of class, I 31 asked my students how their weekend had been. A boy said that his weekend had not been so good. The boy then asked me 32 I always seemed to be so cheerful.
His question 33 me of something I’d read somewhere before, “Every morning when you 34 up, you have a 35 about how you want to face life that day.” I smiled and said to myself, “I choose to be cheerful.”
“Let me give you a(n) 36 ,” I said. “In addition to teaching here, I also teach in another college, 17 miles down the freeway from where I live. A few weeks ago, I 37 those 17 miles to the school. I only had to 38 another quarter mile to reach the school, but then my car 39 . I tried to start it again, but the engine wouldn’t start. So I took my 40 and walked to school.”
“As soon as I got there, I called AAA and arranged for a tow truck(拖车)to meet me at my car 41 class. The headmaster asked me what had happened. ‘This is my 42 day,’ I replied cheerfully. ‘Your car is broken and today is your lucky day?’ she was 43 . ‘What do you mean?’ ‘I live 17 miles from here,’ I replied. ‘My car could have broken down 44 along the freeway, but it didn't. 45 , it broke down in the perfect place: off the freeway and 46 walking distance from here. I’m still able to teach my class, and able to arrange for a tow truck to meet me.’ The headmaster’s eyes were 47 open and then she smiled.”
I 48 the faces in my class. Although it was the early hour, no one seemed to be 49 . My story had 50 them, or maybe it wasn’t the story at all.
31．A．anxiously B．angrily C．sadly D．cheerfully
32．A．why B．how C．that D．whether
33．A．warned B．told C．reminded D．thought
34．A．raise B．keep C．wash D．get
35．A．problem B．choice C．right D．chance
36．A．example B．answer C．story D．explanation
37．A．walked B．ran C．drove D．flew
38．A．stay B．repair C．run D．cover
39．A．burst B．died C．started D．hit
40．A．friends B．books C．ways D．students
41．A．after B．during C．before D．in
42．A．terrible B．great C．lucky D．special
43．A．surprised B．puzzled C．shocked D．amazed
44．A．somewhere B．everywhere C．nowhere D．anywhere
45．A．Instead B．Also C．Then D．Therefore
46．A．at B．within C．beyond D．off
47．A．hardly B．almost C．wide D．quite
48．A．watched B．saw C．made D．scanned
49．A．awake B．asleep C．alone D．cheerful
50．A．controlled B．defeated C．touched D．educated
2Fe2O3+8 SO2，为了提高SO2的生成速率，下列措施可行的是[ ]