ODS (Operational Data Store) are sometimes needed if the source database can not be accessed directly. An ODS also allows you to offload reporting to a 'non-production' datasource, therefore reducing...
I too ran all three queries and only the first and second returned the correct value. I think you have to redo this question with correct possible answers 🙂
I guess we all learn from experience. I for one, had to learn the hard way. After leaving my home computer available for my kids to go on the internet...