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.
正確答案是B，做題的時候A和B猶豫很久，
想請問A為什麼不能選？
考滿分這題沒有解析QQ
謝謝!

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

原文說G島上13種物種跟GF鳥有關沒說這十三種大都發現在G島上

雖然還是不懂，感謝解答

我認為關鍵句應該是：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選項 注意有個now字 文章內並沒有強調及提及的相關內容就不要選

我也是因為樓上那句選B但這句The species on the Galapagos Islands today, most of which occur nowhere else和這句For instance, the Galapagos island chain has atotal of thirteen species of closely related birds called Galapagos finches.讓我好想選A XD