Which is a run-on sentence?
a. when i was picking apples off the tree at dusk, a deer stood at the edge of the orchard.
b. camilla, who was our baby-sitter when we were little, was a contestant on that tv game show.
c. there were big, dark clouds in the sky, on our way home, buckets of rain and hail fell the whole way.
d. if you want to play softball this year, sign-ups are at the field this coming saturday.