As a physician who travels quite

As a physician who travels quite a lot, I spend much time on planes listening to that terrible “Is there a doctor on board?” announcement. I’ve been ___26___ only once-for a woman who had merely fainted. But the ___27___ made me quite curious about how ___28___ this kind of things happens. I wondered what I would do if met with a real midair medical emergency without access ___29___ a hospital staff and the usual emergency equipment. ___30___ the New England Journal of Medicine published a study about if-flight medical events last week. I read it ___31___ interest. The study estimated that there is a sum of 30 in-flight medical emergencies on U.S. flights every day. Most of them are not ___32___ ; fainting and dizziness are the most frequent complains. ___33___ 13% of them-roughly four a day-are serious enough to ___34___ a pilot to change course. The most common of the serious emergencies ___35___ heart trouble, strokes and breathing difficulty. Let’s face it: plane rides are stressful. For starters, cabin pressures at high altitudes (海拔)are set at roughly ___36___ they would be if you lived at 5000 to 8000 feet above sea level. Most people can put up with these pressures pretty ___37___ , but passengers with heart disease ___38___ experience chest pains due to the lack of oxygen flowing through their blood. ___39___ common in-flight problem is the so-called economy class syndrome (综合症). ___40___ happens, don’t panic.
回答第38空
A、ought to
B、may
C、used to
D、need
【正确答案】：B