单项选择题

PRETERNATURAL:

A． invariable
B． truthful
C． delayed
D． reserved
E． commonplace
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单项选择题
It can be inferred from the passage that one reason scientists consider local water from the solar nebula a necessary ingredient in the earth's oceans is that
A． it is improbable that enough volume of water from comets existed to fill the earth's oceans
B． the water from the solar nebula contains less deuterium than sea water
C． the water from the solar nebula existed close enough to the earth to participate in the accretion process
D． without the water from the solar nebula more xenon would otherwise exist in seawater
E． without the water from the solar nebula the earth's oceans would probably have formed at an earlier time
单项选择题
Which of the following, if true, would cast the MOST doubt on scientists' most recent explanation for the origin of the ocean's water
A． Meteorites contain only twice, and not ten times as much xenon as regular sea water.
B． Local water from the solar nebula is found to contain as much xenon as meteorites.
C． Water from the solar nebula contains less deuterium than was previously thought.
D． Comets containing more than twice the amount of deuterium than was previously thought.
E． More than twice as many meteorites as comets existed in the solar system at the time of the Earth's formation.
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