题目内容：

    On the morning of July 4, a magnitude 6.4 earthquake rocked Southern California, destroying roads and sending people fleeing to safety. But that wasn't all the Earth had in store: Less than a day and a half later, a powerful magnitude7. I earthquake shook again. While earthquakes are not unexpected, the two most recent earthquakes are the largest that have struck this area in at least two decades. And a series of large and small aftershocks are expected on the way.

The two earthquakes struck in what's known as the Eastern California shear zone, where the Pacific Plate crushed against the North American Plate. The recent events occurred when two blocks of Earth moved side by side.

They seemed to have occurred along the same set of faults (断层)lying in an area known as the Little Lake fault zone-in most circumstances, earthquakes hit in a familiar order: There's a large earthquake followed by a series of smaller events. That's because the movement that occurs during a large earthquake causes increased force in the surrounding area.

But things are quite different in some circumstances, such as the recent pair of earthquakes in California, a relatively large earthquake just being the forerunner for an even bigger event. While the difference between 7.1 and 6.4 may seem minor，magnitude is a logarithmic (对数的) scale. An increase of a unit of magnitude is about 32 times more energy, which means that the energy the second earthquake released is roughly 11 times that of the first one.

''Fortunately, no deaths or major injuries were reported, '' says Bohon, an earthquake geologist. ''It was in a fairly unpopulated area, although a lot of people felt it'' She suggests people who live in earthquake-prone (地震频发的)areas check how prepared they are for the next event. And she also hopes that the earthquake early warning system can play a good role in saving tens of thousands of lives and schools will popularize the knowledge of geological (地质的) disasters among students.

1.What can be learned from the first two paragraphs?

A.The first earthquake was predicted before its occurrence.

B.The two big earthquakes hit the same area within one day.

C.The aftershocks are even more dangerous than the first two earthquakes.

D.The second earthquake is the largest one in Southern California since 2000.

2.What does the third paragraph mainly talk about?

A.The introduction of Eastern California shear zone.

B.The forming process of the Little Lake fault zone.

C.The geological facts about the two big earthquakes.

D.The potential disasters caused by plate movement.

3.The recent two earthquakes represent an unusual circumstance in the way that.

A.a major earthquake is followed by a larger one

B.there is a minor difference in their magnitude

C.the two earthquakes release a similar amount of energy

D.a series of smaller earthquakes occur in the surrounding areas

4.What contributes to the good point of the two Southern California earthquakes?

A.The popularization of earthquake knowledge in schools.

B.Peopled good preparation made in advance.

C.Small populations in the earthquake-hit area.

D.The earthquake early warning system.