12. According to paragraph 6, what is true about the thirteen species of
Galapagos finches?
(A)All thirteen species are now found on most of the Galapagos Islands.
(B)All thirteen species are descended from the same population of ancestral
birds.
Paragrapg 6:
The species on the Galapagos Islands today, most of which occur nowhere else,
descended from organisms that floated, flew, or were blown over the sea from
the South American mainland. For instance, the Galapagos island chain has a
total of thirteen species of closely related birds called Galapagos finches.
These birds have many similarities but differ in their feeding habits and
their beak type, which is correlated with what they eat. Accumulated evidence
indicates that all thirteen finch species evolved from a single small
population of ancestral birds that colonized one of the islands. Completely
isolated on the island after migrating from the mainland, the founder
population may have undergone significant changes in its gene pool and become
a new species. Later, a few individuals of this new species may have been blow
n
a neighboring island.Isolated on this second island, the second founder
population could have evolved into a second new species, which could later
recolonize the island from which its founding population emigrated. Today
each Galapagos island has multiple species of finches, with as many as ten on
some islands.
正确答案是B，做题的时候A和B犹豫很久，
想请问A为什么不能选？
考满分这题没有解析QQ
谢谢!

Non mentioned？All thirteen species are now "found" on most of the Galapagos Islands.

原文说G岛上13种物种跟GF鸟有关没说这十三种大都发现在G岛上

虽然还是不懂，感谢解答

我认为关键句应该是：Accumulated evidenceindicates that all thirteen finch species evolved from a single smallpopulation of ancestral birds that colonized one of the islands.但注意A选项 注意有个now字 文章内并没有强调及提及的相关内容就不要选

我也是因为楼上那句选B但这句The species on the Galapagos Islands today, most of which occur nowhere else和这句For instance, the Galapagos island chain has atotal of thirteen species of closely related birds called Galapagos finches.让我好想选A XD