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Hotter and more massive than the Sun, stars called “stragglers” are puzzling to astronomers because such rapidly burning stars would not be expected to persist in ancient star clusters. Some researchers believe that the typical blue stragglers formed when two ancient, lower-mass stars collide and merge form more massive, hotter star. Peter Leonard theorizes alternatively that in low density globular clusters, where mergers between single stars occur too infrequently to account for the observed quantity of blue stragglers, these stragglers are created instead by a group of stars. He suggests that a pair of stars already orbiting each other presents a larger target for a third star or another pair. Once this new grouping forms, close encounters between the stars could prompt any two to merge as a blue straggler. Leonard’s model predicts that each blue straggler has a distant orbiting companion —as appears true of many blue stragglers in the M67 cluster of the Milky Way galaxy.

The reference to a “larger target” serves primarily to suggest why

Ablue straggler would be more likely to collide and merge with another star than would be a lower-mass star.
Bpair of stars would be more likely to encounter other stars than would the typical blue straggler.
Cpair of stars would be more likely to interact with other stars than would a single star
Dblue straggler would be more likely to interact with a pair of stars than it would with a third star.
Ethird star would be more likely to encounter a pair than it would to encounter a blue straggler.
Select one answer choice.
正确答案:C
详解
定位第四句。文中出现large target ,是指a pair of stars 更容易成为第三颗恒星或者其它“pair stars”的目标,进一步解释上文Peter Leonard的理论:单个恒星的合并发生得不频繁,不能解释blue straggler的出现。
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