Prep2012_Pack1_RC(题目版)(5)

The author states that the research described in the first paragraph was undertaken in order to

A. determine the age of an actual meteor stream

B. dentify the various structural features of meteor streams

C. explore the nature of a particularly interesting meteor stream

D. test the hypothesis that meteor streams become broader as they age

E. show that a computer model could help in explaining actual astronomical data

PREP2012-Pack1-RC-002-02 VRC07544-02 Hard

It can be inferred from the passage that which of the following would most probably be observed during the Earth's passage through a meteor stream if the conventional theories mentioned in the highlighted text were correct?

A. Meteor activity would gradually increase to a single, intense peak, and then gradually

decline.

B. Meteor activity would be steady throughout the period of the meteor shower.

C. Meteor activity would rise to a peak at the beginning and at the end of the meteor shower.

D. Random bursts of very high meteor activity would be interspersed with periods of very

activity.

E. In years in which the Earth passed through only the outer areas of a meteor stream,

meteor activity would be absent.

PREP2012-Pack1-RC-002-03 VRC07544-03 Hard

According to the passage, why do the dust particles in a meteor stream eventually surround a comet's original orbit?

A. They are ejected by the comet at differing velocities.

B. Their orbits are uncontrolled by planetary gravitational fields.

C. They become part of the meteor stream at different times.

D. Their velocity slows over time.

E. Their ejection velocity is slower than that of the comet.

PREP2012-Pack1-RC-002-04 VRC07544-04 Hard

The passage suggests that which of the following is a prediction concerning meteor streams that can be derived from both the conventional theories mentioned in the highlighted text and the new computer derived theory?

A. Dust particles in a meteor stream will usually be distributed evenly throughout any cross

section of the stream.

B. The orbits of most meteor streams should cross the orbit of the Earth at some point and

give rise to a meteor shower.

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