A personal care direct-to-consumer brand is considering testing paid advertising channels for user growth. From the list below, identify the factor(s) that are relevant for effectively testing these channels:
- Factor I: Alignment with the brand's average revenue per user (ARPU).
- Factor II: Engagement rates on the brand's social media organic posts.
- Factor III: Measuring conversion rates and return on ad spend (ROAS) from the campaigns.
- Factor IV: Frequency of blog content updates on the brand's website.
Select the relevant factor(s) for testing Paid Advertising Channels.