请教gwd-23-2

卡通猫王

Q2:

Known today by a name they would not have recognized—Anasazi, Navajo for “ancient enemies”—the ancestors of the modern Zuni and Hopi built and then, for reasons still mysterious, abandoned the complex roads and structures of the domain they ruled a millennium ago in the American southwest.

1. ancestors of the modern Zuni and Hopi built and then, for reasons still mysterious, abandoned the complex roads and structures of the domain they ruled a millennium ago in the American southwest

2. reasons are still mysterious why the ancestors of the modern Zuni and Hopi built and then abandoned the complex roads and structures of the domain they ruled in the American southwest a millennium ago

3. modern Zuni and Hopi had ancestors who, a millennium ago, ruled a domain in the American southwest where they built and then abandoned complex roads and structures for still mysterious reasons

4. domain of the American southwest was ruled a millennium ago by the ancestors of the modern Zuni and Hopi, who built and then, for reasons still mysterious, abandoned complex roads and structures

5. complex roads and structures of the domain that the ancestors of the modern Zuni and Hopi ruled a millennium ago in the American southwest were built and then, for reasons still mysterious, abandoned

   Answer: a

请哪位牛人说说选A的主要原因，C也没什么问题啊

periodic

ancestors is  the reason why A is correct.  the word "Known" at the beginning of the sentence is to modify them.