完型填空（共20小题；每小题1.5分，满分30分）
阅读下面短文，掌握其大意，然后从36—55各题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上涂黑。
As a physician who travels quite a lot, I spend a lot of time on planes listening for that dreaded “Is there a doctor on board?” announcement. I’ve been
36 only once-for a woman who had merely fainted. But the
37 made me quite curious about how
38 this kind of thing happens. I wondered what I would do if
39 with a real mid-air medical emergency-without access
40 a hospital staff and the usual emergency equipment. So 41 the New England Journal of Medicine last week
42 a study about in-flight medical events, I 43 it with interest.
The study estimated that there are a(n)
44 of 30 in-flight medical emergencies on U.S. flights every day. Most of them are not
45 ; fainting and dizziness are the most frequent complaints.
46 13% of them-roughly four a day-are serious enough to
47 a pilot to change course. The most common of the serious emergencies 48 heart trouble, strokes, and difficult breathing.
Let’s face it: plane rides are
49 . For starters, cabin pressures at high altitudes are set at roughly
50 they would be if you lived at 5,000 to 8,000 feet above sea level. Most people can tolerate these pressures pretty
51 , but passengers with heart disease
52 experience chest pains as a result of the reduced amount of oxygen flowing through their blood.
53 common in-flight problem is deep venous thrombosis（血栓）-the so-called economy class syndrome（综合症）.
54 happens, don’t panic. Things are getting better on the in-flight emergency front. Thanks to more recent legislation（立法）, flights with at
55 one attendant are starting to install emergency medical equipments to treat heart attacks.
36. A. called B. informed C. addressed D. surveyed
37. A. accident B. incident C. condition D. disaster
38. A. soon B. many C. long D. often
39. A. met B. identified C. treated D. provided40. A. for B. by C. to D. through
41. A. before B. when C. since D. while
42. A. collected B. discovered C. conducted D. published
43. A. consulted B. read C. consumed D. considered
44. A. amount B. sum C. average D. number
45. A. significant B. common C. heavy D. serious
46. A. For B. But C. And D. So
47. A. require B. engage C. inspire D. command
48. A. include B. imply C. confine D. contain
49. A. enjoyable B. favorable C. peaceful D. stressful
50. A. who B. which C. what D. that
51. A. mentally B. easily C. neatly D. naturally
52. A. ought to B. used to C. may D. need
53. A. Any B. Other C. One D. Another
54. A. Whatever B. Whenever C. Whichever D. Wherever
55. A. most B. least C. worst D. best
的是___________。