Answer: You've seen a 7-percent increase in online sales.
Step-by-step explanation:
A 7-percent increase in online sales will iindicate that the user-generated content is getting a better response.
Option A is Incorrect as 3,000 users posting photos or videos doesn't indicate that there social media strategy used is working for the company.
Option B and C isn't correct as well. Option D shows that the social media strategy is having a positive impact as there's an increase in sales.