单项选择题

We all know that a magician does not really depend on "magic" to perform his tricks, (31) on his ability to act at great speed. (32) , this does not prevent us from enjoying watching a magician (33) rabbits from a hat. (34) the greatest magician of all time was Harry Houdini who died in 1926. Houdini mastered the art of (35) . He could free himself from the tightest knots or the most complicated locks in seconds. (36) no one really knows (37) he did this, there is no doubt (38) he had made a close study of every type of lock ever (39) . He liked to carry a small steel needle-like tool strapped to his leg and he used this in (40) of a key. Houdini once asked the Chicago police to lock him in prison. They (41) him in chains and locked him up, but he freed himself (42) an instant. The police (43) him of having used a tool and locked him up again. This time he wore no clothes and there were chains round his neck, waist, wrists, and legs; but he again escaped in a few minutes. Houdini had probably hidden his "needle" in a wax-like (44) and dropped it on the floor in the passage. (45) he went past, he stepped on it so that it stuck to the bottom of his foot. His most famous escape, however, was (46) astonishing. He was heavily chained (47) and enclosed in an empty wooden chest, the lid of (48) was nailed down. The (49) was dropped into the sea in New York harbor. In one minute Houdini had swum to the surface. When the chest was (50) , it was opened and the chains were found inside.