How to figure out the main idea of a story

Which does not contain a run-on sentence? a. in the late autumn, my grandmother cooks an amazing pie she uses acorn squash and fresh honey. b. in the late autumn, my grandmother cooks an amazing pie she uses, acorn squash and fresh honey. c. in the late autumn, my grandmother cooks she makes an amazing pie with acorn squash and fresh honey. d. in the late autumn, my grandmother cooks an amazing pie with acorn squash and fresh honey.