[单项选择]Man has long wished to predict earthquakes. Recent findings indicate that reliable earthquake prediction is almost a reality. Before earthquakes occur, there frequently are changes in rock behavior that affect the velocities of other earthquake waves passing through the rocks. The former Soviet seismologists have used earthquake waves from other unrelated earthquakes to meas- ure the alterations in wave speed through rocks around a fault zone. For months to years before a particular earthquake, the former Soviet scientists observed that the strained rock in the fault zone was deformed in a way that slowed other earthquake wave that passed through the zone. Similar behavior has preceded earthquakes in California and New York.
Changes in electrical resistance, water pressure l rock motion, and leakage of gas also can accompany the lowering of wave velocity. Fractures in the fault zone apparently open, which leads to a lowering of water pressure. When the fractures are filled by unde
A. a certain major destructive quake can be avoided by prediction
B. American scientists have achieved more in earthquake prediction
C. careful observations of preliminary events can lead to reliable prediction
D. scientists can predict the coming quake exactly

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