From a quick search, here's what I discovered.
To analyze the complaints in the CSV file by the logged date and use a built-in date hierarchy, you should apply a transformation to extract the first 11 characters of the logged column. This action will isolate the date part of the 'Logged' column (e.g., '2018-12-31'), which is suitable for date hierarchy analysis. This approach is effective as it maintains the date in a recognizable format while discarding the time part, which may not be necessary for your date hierarchy analysis. This method ensures that you can analyze the data by year, month, and day without unnecessary complications.
For further detailed steps and examples, you can refer to Microsoft's documentation on Power BI and data transformation techniques, such as Power BI Desktop - Add Column From Example and Power Query - Split Date and Time into Separate Columns. the answer is A