原题
Twin Stars
Stars form in the relatively dense, egg-shaped cores of molecular clouds made of dust and gases. Scientists mapping these dense cores must use radio waves to penetrate the dust and gases that prevent light from escaping molecular clouds; satellite images of these regions show nothing but large, black areas of space.
Recent observations of the Perseus molecular cloud may have surprising implications for previously accepted conclusions about the Sun. A radio wave sweep of the Perseus cloud's dense cores revealed that the youngest stars existing in the cloud all occurred in pairs, or binary twins, orbiting a common point. Stars of older binary systems, of which there were fewer, appeared closer together than stars of younger binary systems.
Scientists used current knowledge about stellar growth, decay, and destruction to predict the paths along which binary stars traveled throughout the molecular cloud. Their estimates would align with current understandings only if all stars approximately the same size as the Sun had begun as members of a binary system that first moved closer to each other and later separated. This rule would also apply to the Sun, whose twin likely separated following approximately one million years of coexistence.
What do the "estimates" discussed in the passage refer to?
AThe rate at which stars grow in the molecular cloud
BThe course that stars move along within the molecular cloud
CThe number of binary star systems found in the molecular cloud
DThe number of stars that have formed within the molecular cloud
正确答案：B
解题思路
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