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

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单项选择题

The author implies that scientists who regard the notion of a final state of truth without skepticism are Ⅰ. More arrogant or unimaginative than scientists who see science as a perpetual process Ⅱ. Visionaries who, though not necessarily correct, maintain an optimistic view of the future Ⅲ. A very significant majority of the scientific community

(A) Ⅰ only
(B) Ⅱ only
(C) Ⅰ and Ⅲ only
(D) Ⅱ and Ⅲ only
(E) Ⅰ, Ⅱ, and Ⅲ

单项选择题

According to the passage, scientists have concluded which of the following from the discovery of the large amount of deuterium found in comets

(A) Comets do not contain enough deuterium to have solely created the Earth’s oceans.
(B) Given the ratio of deuterium to ordinary hydrogen in seawater, comets cannot have contributed to the Earth’s oceans.
(C) It is likely that comets contain less Xenon than meteorites do.
(D) Given the low level of deuterium in the waters of Earth’s oceans, comets cannot be its sole source.
(E) Comets now play a greater role in the creation of the Earth’s oceans than was previously thought.