Answer:
The correct answer is option D. The revision that most effectively corrects the fused sentence is "Track is important to Greg, so he runs several times a week."
Step-by-step explanation:
The sentence is the correct way to do the revision as it adds a punctuation colon that helps to separate the different parts of the sentence. On the first half of it is stated the importance that track has for Greg, and on the second half of the sentence after the colon, it is described what Greg does in order to show commitment and dedication to track, with the two parts of the sentence connected by the colon and the adverb "so".