D) Because of the rich natural resources which made the Sacramento Valley a ‘Garden of Eden,’ Native Americans established permanent villages there 8,000 years ago.
Option D is the best choice. While some of the other options correctly join the two ideas together, they do not achieve a coherent flow of ideas. The use of the conjunction "because" and the addition of "Native Americans" to eliminate passive voice help to create this flow. Now it is clear who established permanent villages and why this fact about the Sacramento Valley being a 'Garden of Eden' is relevant.