The interstellar clouds called molecular clouds are
A) the clouds in which elements such as carbon, nitrogen, and oxygen are made.
B) clouds that are made mostly of complex molecules such as carbon dioxide and sulfur dioxide.
C) the hot clouds of gas expelled by dying stars.
D) the cool clouds in which stars form.
Question 2
Why are the inner planets made of denser materials than the outer planets?
A) The Sun's gravity pulled denser materials toward the inner part of the solar nebula, while lighter gases escaped more easily.
B) Denser materials were heavier and sank to the center of the nebula.
C) In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions.
D) When the solar nebula formed a disk, materials naturally segregated into bands, and in our particular solar system the denser materials settled nearer the Sun while lighter materials are found in the outer part.
E) In the beginning, when the protoplanetary disk was spinning faster, centrifugal forces flung the lighter materials toward the outer parts of the solar nebula.
Phenotypic and molecular markers mapped on human chromosome 1
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Growth in Cold and Cool Clouds
Growth in Cold and Cool Clouds
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