[单项选择]Friedrich Dobl, a Yugoslav working in Germany, was fed up with traffic jams. At long weekends and holiday times when he wanted to (47)______ quickly, he always found himself behind hundreds of other cars moving (48)______ along the notorious foreign workers route through Germany and Austria. How easy it all was for police and emergency services. A siren, a flashing light And like magic everyone was (49)______ of the way. Going home from work one night he passed a garage. And there in front of him was the answer to his problem. An old ambulance was (50)______. The red cross had been removed, but not the flashing light, and the (51)______. He tried the light. It flashed magnificently. He tried the siren. That too sounded impressive. He bought the (52)______ and opened up for himself a dream world of motoring. It began early in the morning, all his luggage in the back of the ambulance and motorway in Germany looking reasonably clear. Soon, as always, a lone line of traffic (53)_