A digital marketing manager at a leading e-commerce platform is faced with several tasks to improve the company's performance. Consider the following tasks and determine which involve Root Cause Analysis:
- Task I: Investigating the reasons behind a sudden decrease in user engagement on the platform.
- Task II: Comparing the monthly sales data of the current year to the previous year to note the trend.
- Task III: Examining why a particular product line has significantly higher return rates compared to others.
Choose the combination that accurately identifies the tasks involving Root Cause Analysis.