13.
Your Answer is
Correct Answer is D
Explanation
Item B/C: The subject is Two runner and dogs, the predicate is came, the sentence meaning "two runners approaching and their dirty but friendly dog ??came here...", apply their here, B/C mistake.
Item A: Scruffy "adj. Dirty" and friendly "adj. Friendly" are juxtaposed to modify dogs together, so A is wrong (scruffily is an adverb).