請問一題文法題？

[rukawa]

Many wild animals, without ample vegetation to feed on,

they move everywhere, and their predators follow.
答案是they move 錯誤，不合文法，請問是為什麼？

請問,without ample vegetation to feed on,是介系詞片語嗎？
為什麼這句話的兩邊都要有逗點，請問這是什麼規則？
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☆ [Origin:椰林風情] [From: 218-162-189-184.dynamic.hin] [Login: **] [Post: 39]

[John Doe]

Post by rukawa
Many wild animals, without ample vegetation to feed on,
they move everywhere, and their predators follow.
答案是they move 錯誤，不合文法，請問是為什麼？

Many wild animals move everywhere, and their....
不需要 they

Post by rukawa
請問,without ample vegetation to feed on,是介系詞片語嗎？
為什麼這句話的兩邊都要有逗點，請問這是什麼規則？

這是屬於一種補充性的解釋前述名詞/子句內容的用法，在學術性
文章，教科書之類的地方很常用。