单选题 He shouldn't have come back alive. Captain J. H. Hedley was British pilot in World War I. He fell victim to a bit of misfortune that would have been enough to kill anyone. Yet, with bad luck staring him in the face, good luck was coming up fast on his tail.
Captain Hedley was flying a mission over Germany with his copilot, A Canadian flyer named Makepeace. Suddenly they were surrounded by a group of German fighters. Makepeace, an experienced pilot, knew he had to take the plane into a vertical dive in order to slip away from Germans. Inexplicably, Hedley was caught unaware by his copilot's maneuver. He was thrown sharply out of his seat and out of the plane. Makepeace sadly counted Hedley a dead man and continued his evasive maneuvers.
Suddenly, Makepeace spotted Hedley clinging to the tail of the plane, Hedley hung on and pulled himself back into the plane when it leveled off. Makepeace was stunned by the sight of Hedley, but he kept his composure enough to get them out of the trouble and out of Germany. The best explanation for Hedley's reprieve(缓刑) was that the plane's sudden vertical dive had created a vacuum in the air be- hind it. Hedley fell into the vacuum and was pulled along until he grabbed the tail and made his fantastic reentry.

单选题 In World War I, British and Canada were______.

单选题 We can conclude that Hedley's escape from death was mostly due to ______.

单选题 The writer begins the passage by ______.

单选题 Something inexplicable is ______.