Sentence Correction

Politicians and philosophers, early forms of democratic government and public discourse were pioneered by the ancient Greeks, laying the groundwork for much of modern society.

(A) early forms of democratic government and public discourse were pioneered by the ancient Greeks, laying the groundwork for much of modern society

(B) laying the groundwork for much of modern society, early forms of democratic government and public discourse were pioneered by the ancient Greeks

(C) the ancient Greeks pioneered early forms of democratic government and public discourse, laying the groundwork for much of modern society

(D) there were pioneered, laying the groundwork for much of modern society, early forms of democratic government and public discourse by the ancient Greeks

(E) were the ancient Greeks who, laying the groundwork for much of modern society, pioneered early forms of democratic government and public discourse

The OA is C.

This question confused me. The 5 choices are different from each other. I couldn't determine the correct option.