Answer by Alendar

"first table Member ([MemID], MemName, ActivityID) Second table Activity ([ActivityID], ActName, SesID) Third table Session ([SesID], Day, From, To, CoachID) Fourth table Coach ([CoachID], Name)" is incorrect. It states that one member can only ever engage in a single activity, which is incorrect. "Session" is your clue. What do sessions have? Times. They happen at times and involve people, places, and things. They are transactional. This is your fact table. All others are referential. The reference tables Member, Activity, and Coach are not related to each other. Think of Session as being a grab bag that pulls all the others together for a party.