[单项选择]奇经八脉有"一源三歧"现象。其源是指：（）。
A. 膀胱
B. 胆
C. 胞宫
D. 脑
E. 脉

Earthquake is a shaking of the ground caused by the sudden breaking and the shifting of large sections of the earth’s rocky outer shell. Earthquakes are among the most powerful events on earth, and their results can be terrifying. A severe earthquake may release energy 10,000 times as great as that of the first atomic bomb. Rock movements during an earthquake can make rivers change their courses. Earthquakes can trigger landslides that cause great damage and loss of life. Large earthquakes beneath the ocean can create a series of huge, destructive waves called tsunamis that flood coasts for many miles.
Earthquakes almost never kill people directly. Instead, many deaths and injuries in earthquakes result from falling objects and the collapse of buildings, bridges, and other structures. Fire resulting from broken gas or power lines is another major danger during a quake. Spills of hazardous chemicals are also a concern during an earthquake.
(77) The
A. people are killed and injured
B. rocks are breaking and shifting
C. destructive waves flood the coasts for miles
D. large sections of the earth’s rocky outer shell suddenly break and shift